feat(unity): Attachment docs (#4493)

* tweaked attachment docs to be more unity specific

* removed redundant comment

Author: bitsandfoxes

src/includes/enriching-events/attachment-init-with-path/unity.mdx

@@ -0,0 +1,10 @@
+```csharp
+using Sentry;
+
+SentrySdk.ConfigureScope(scope =>
+{
+    scope.AddAttachment(Path.Combine(Application.persistentDataPath, "file.log"));
+});
+```
+
+Note that there are restrictions in place when using paths in combination with [StreamingAssets](https://docs.unity3d.com/2019.4/Documentation/Manual/StreamingAssets.html) and the [Resource folder](https://docs.unity3d.com/ScriptReference/Resources.html).

src/includes/enriching-events/attachment-upload/unity.mdx

@@ -1,13 +1,11 @@
 ```csharp
 using Sentry;
 
-// Global Scope
 SentrySdk.ConfigureScope(scope =>
 {
-    scope.AddAttachment("log.txt");
+    scope.AddAttachment(Path.Combine(Application.persistentDataPath, "file.log"));
 });
 
-// Clear all attachments in the global scope
 SentrySdk.ConfigureScope(scope =>
 {
     scope.ClearAttachments();

src/platforms/common/enriching-events/attachments/index.mdx

@@ -86,14 +86,22 @@ You'll first need to import the SDK, as usual:
 
 </PlatformSection>
 
-<PlatformSection supported={["android", "apple", "java", "dotnet", "dart", "flutter"]}>
+<PlatformSection notSupported={["unity"]} supported={["android", "apple", "java", "dotnet", "dart", "flutter"]}>
 
 Attachments live on the <PlatformLink to="/enriching-events/scopes/">Scope</PlatformLink>. You can either add an attachment on the global scope to be sent with every event or add it on the <PlatformLink to="/enriching-events/scopes/#local-scopes">local Scope</PlatformLink> to just send the attachment with one specific event.
 
 <PlatformContent includePath="enriching-events/attachment-upload" />
 
 </PlatformSection>
 
+<PlatformSection supported={["unity"]}>
+
+Unity features a global <PlatformLink to="/enriching-events/scopes/">scope</PlatformLink> to which you add an attachment that will be sent with every event.
+
+<PlatformContent includePath="enriching-events/attachment-upload" />
+
+</PlatformSection>
+
 <Note>
 
 Sentry allows at most 100MB of attachments per event, including the crash report file (if applicable) Uploads exceeding this size are rejected with HTTP error `413 Payload Too Large` and the data is dropped immediately. To add larger or more files, consider secondary storage options.