Document why examples are disabled on the web, pass 1 (#19262)

# Objective

With the Bevy CLI, we now have an easy way to locally test if examples
work on the web.
We should start to explicitly document why examples don't work on the
web to keep track and to ensure that as many examples are enabled as
possible.

## Solution

- Go through the examples with `wasm = false` and check if they really
don't work
- If they don't work, try to figure out why by looking through the code
and announcement posts (we need better docs for this please) and add a
comment explaining it
- The `lightmap` example seemed to work without problems, so I enabled
it

## Testing

Install the [Bevy CLI](https://github.com/TheBevyFlock/bevy_cli) and
run:

```
bevy run --example={example_name} web --open
```

# Future Work

- There are about 100 more examples with `wasm = false` that also need
to be documeneted
- Also improve the documentation on the related features/plugins/types
to make it easier for users to determine what they can use

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: IceSentry <IceSentry@users.noreply.github.com>

Author: 3 people

Cargo.toml

@@ -868,6 +868,7 @@ doc-scrape-examples = true
 name = "Texture Atlas"
 description = "Generates a texture atlas (sprite sheet) from individual sprites"
 category = "2D Rendering"
+# Loading asset folders is not supported in Wasm, but required to create the atlas.
 wasm = false
 
 [[example]]
@@ -945,6 +946,7 @@ doc-scrape-examples = true
 name = "2D Wireframe"
 description = "Showcases wireframes for 2d meshes"
 category = "2D Rendering"
+# PolygonMode::Line wireframes are not supported by WebGL
 wasm = false
 
 # 3D Rendering
@@ -1012,6 +1014,7 @@ doc-scrape-examples = true
 name = "Anti-aliasing"
 description = "Compares different anti-aliasing methods"
 category = "3D Rendering"
+# TAA not supported by WebGL
 wasm = false
 
 [[example]]
@@ -1056,6 +1059,7 @@ doc-scrape-examples = true
 name = "Auto Exposure"
 description = "A scene showcasing auto exposure"
 category = "3D Rendering"
+# Requires compute shaders, which are not supported by WebGL.
 wasm = false
 
 [[example]]
@@ -1123,6 +1127,7 @@ doc-scrape-examples = true
 name = "Screen Space Ambient Occlusion"
 description = "A scene showcasing screen space ambient occlusion"
 category = "3D Rendering"
+# Requires compute shaders, which are not supported by WebGL.
 wasm = false
 
 [[example]]
@@ -1222,6 +1227,7 @@ doc-scrape-examples = true
 name = "Order Independent Transparency"
 description = "Demonstrates how to use OIT"
 category = "3D Rendering"
+# Not supported by WebGL
 wasm = false
 
 [[example]]
@@ -1321,7 +1327,7 @@ doc-scrape-examples = true
 name = "Skybox"
 description = "Load a cubemap texture onto a cube like a skybox and cycle through different compressed texture formats."
 category = "3D Rendering"
-wasm = false
+wasm = true
 
 [[example]]
 name = "solari"
@@ -1432,6 +1438,7 @@ doc-scrape-examples = true
 name = "Wireframe"
 description = "Showcases wireframe rendering"
 category = "3D Rendering"
+# Not supported on WebGL
 wasm = false
 
 [[example]]
@@ -1443,6 +1450,8 @@ doc-scrape-examples = true
 name = "Irradiance Volumes"
 description = "Demonstrates irradiance volumes"
 category = "3D Rendering"
+# On WebGL and WebGPU, the number of texture bindings is too low
+# See <https://github.com/bevyengine/bevy/issues/11885>
 wasm = false
 
 [[example]]
@@ -1455,6 +1464,7 @@ required-features = ["meshlet"]
 name = "Meshlet"
 description = "Meshlet rendering for dense high-poly scenes (experimental)"
 category = "3D Rendering"
+# Requires compute shaders and WGPU extensions, not supported by WebGL nor WebGPU.
 wasm = false
 setup = [
   [
@@ -1490,7 +1500,7 @@ doc-scrape-examples = true
 name = "Lightmaps"
 description = "Rendering a scene with baked lightmaps"
 category = "3D Rendering"
-wasm = false
+wasm = true
 
 [[example]]
 name = "no_prepass"
@@ -1643,6 +1653,7 @@ doc-scrape-examples = true
 name = "Custom Loop"
 description = "Demonstrates how to create a custom runner (to update an app manually)"
 category = "Application"
+# Doesn't render anything, doesn't create a canvas
 wasm = false
 
 [[example]]
@@ -1654,6 +1665,7 @@ doc-scrape-examples = true
 name = "Drag and Drop"
 description = "An example that shows how to handle drag and drop in an app"
 category = "Application"
+# Browser drag and drop is not supported
 wasm = false
 
 [[example]]
@@ -1665,6 +1677,7 @@ doc-scrape-examples = true
 name = "Empty"
 description = "An empty application (does nothing)"
 category = "Application"
+# Doesn't render anything, doesn't create a canvas
 wasm = false
 
 [[example]]
@@ -1688,6 +1701,7 @@ required-features = ["bevy_log"]
 name = "Headless"
 description = "An application that runs without default plugins"
 category = "Application"
+# Doesn't render anything, doesn't create a canvas
 wasm = false
 
 [[example]]
@@ -1710,6 +1724,8 @@ doc-scrape-examples = true
 name = "Log layers"
 description = "Illustrate how to add custom log layers"
 category = "Application"
+# Accesses `time`, which is not available on the web
+# Also doesn't render anything
 wasm = false
 
 [[example]]
@@ -1721,6 +1737,7 @@ doc-scrape-examples = true
 name = "Advanced log layers"
 description = "Illustrate how to transfer data between log layers and Bevy's ECS"
 category = "Application"
+# Doesn't render anything, doesn't create a canvas
 wasm = false
 
 [[example]]