Add Github Action: PR labeler (#669)

Adds automatic labeling to pull requests

.github/labeler.yml

@@ -0,0 +1,18 @@
+#levels
+levels:
+  - levels/**/*
+#sprites
+sprites:
+  - sprites/**/*
+#music
+music:
+  - musics/**/*
+#sounds:
+sounds:
+  - sounds/**/*
+#patches:
+patches:
+  - patches/**/*
+#flats:
+flats:
+  - flats/**/*

.github/workflows/label.yml

@@ -0,0 +1,17 @@
+# This workflow will triage pull requests and apply a label based on the
+# paths that are modified in the pull request.
+#
+# To use this workflow, you will need to set up a .github/labeler.yml
+# file with configuration.  For more information, see:
+# https://github.com/actions/labeler/blob/master/README.md
+
+name: Labeler
+on: [pull_request]
+
+jobs:
+  label:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/labeler@v2
+      with:
+        repo-token: "${{ secrets.GITHUB_TOKEN }}"