Add script to generate changelogs (#2920)

* Add script to generate changelogs from PR labels

* Improve PR template

* Better categorization

.github/pull_request_template.md

@@ -3,8 +3,8 @@ Please read the "Making a PR" section of [`CONTRIBUTING.md`](https://github.com/
 
 * Keep your PR:s small and focused.
 * If applicable, add a screenshot or gif.
-* Unless this is a trivial change, add a line to the relevant `CHANGELOG.md` under "Unreleased".
-* If it is a non-trivial addition, consider adding a demo for it to `egui_demo_lib`.
+* If it is a non-trivial addition, consider adding a demo for it to `egui_demo_lib`, or a new example.
+* Do not open PR:s from your `master` branch, as thart makes it difficult for maintainers to add commits to your PR.
 * Remember to run `cargo fmt` and `cargo clippy`.
 * Open the PR as a draft until you have self-reviewed it and run `./scripts/check.sh`.
 * When you have addressed a PR comment, mark it as resolved.

.github/workflows/labels.yml

@@ -0,0 +1,32 @@
+# https://github.com/marketplace/actions/require-labels
+# Check for existence of labels
+# See all our labels at https://github.com/rerun-io/rerun/issues/labels
+
+name: Pull Request Labels
+
+on:
+  pull_request:
+    types:
+      - opened
+      - synchronize
+      - reopened
+      - labeled
+      - unlabeled
+
+jobs:
+  label:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check for a "do-not-merge" label
+        uses: mheap/github-action-required-labels@v3
+        with:
+          mode: exactly
+          count: 0
+          labels: "do-not-merge"
+
+      - name: Require at least one label
+        uses: mheap/github-action-required-labels@v3
+        with:
+          mode: minimum
+          count: 1
+          labels: "ecolor, eframe, egui_extras, egui_glow, egui-wgpu, egui-winit, egui, epaint"