chore: Convert pull request template to a form (#991)

Author: claremacrae

.github/PULL_REQUEST_TEMPLATE/pull-request.yaml

@@ -0,0 +1,80 @@
+name: Pull Request
+description: Contribute an improvement - new, improved form!
+labels:
+body:
+  - type: markdown
+    attributes:
+      value: |
+        Provide a general summary of your changes in the Title above.
+
+  - type: textarea
+    id: description
+    attributes:
+      label: Description
+      description: Describe your changes in detail.
+    validations:
+      required: true
+
+  - type: textarea
+    id: motivation-and-context
+    attributes:
+      label: Motivation and Context
+      description: |
+        Why is this change required? What problem does it solve?
+        If it fixes any open issue, please link to the issue here.
+    validations:
+      required: true
+
+  - type: textarea
+    id: testing
+    attributes:
+      label: How has this been tested?
+      description: |
+        Please describe in detail how you tested your changes.
+        Include details of your testing environment, tests ran to see how your change affects other areas of the code, etc.
+    validations:
+      required: true
+
+  - type: textarea
+    id: screenshots
+    attributes:
+      label: Screenshots (if appropriate)
+      description: |
+        Paste in any useful screenshots, with descriptions.
+    validations:
+      required: true
+
+  - type: checkboxes
+    id: types-of-changes
+    attributes:
+      label: Types of changes
+      description: What types of changes does your code introduce? Select all that apply.
+      options:
+        - label: Bug fix (non-breaking change which fixes an issue)
+        - label: Refactor (non-breaking change which only improves the design or structure of existing code, and making no changes to its external behaviour)
+        - label: New feature (non-breaking change which adds functionality)
+        - label: Breaking change (fix or feature that would cause existing functionality to not work as expected)
+
+  - type: checkboxes
+    id: checklist
+    attributes:
+      label: Checklist
+      description: |
+        Go over all the following points, and select all that apply.
+        If you're unsure about any of these, don't hesitate to ask. We're here to help!
+      options:
+        - label: My code follows the code style of this project and passes `yarn run lint`.
+        - label: My change requires a change to the documentation.
+        - label: I have updated the documentation accordingly.
+        - label: My change has adequate Unit Test coverage.
+
+  - type: checkboxes
+    id: terms
+    attributes:
+      label: Code of Conduct
+      description: By submiting this pull request, you agree to follow our [contributing guide](https://github.com/obsidian-tasks-group/obsidian-tasks/blob/main/CONTRIBUTING.md) and [Code of Conduct](https://github.com/obsidian-tasks-group/obsidian-tasks/blob/main/CODE_OF_CONDUCT.md).
+      options:
+        - label: My contribution follow this project's [contributing guide](https://github.com/obsidian-tasks-group/obsidian-tasks/blob/main/CONTRIBUTING.md)
+          required: true
+        - label: I agree to follow this project's [Code of Conduct](https://github.com/obsidian-tasks-group/obsidian-tasks/blob/main/CODE_OF_CONDUCT.md)
+          required: true