ci: auto-add labels on issues based on title

This is similar to the pull request labeler. We search for certain key words in
the issue title and add them if they are present.

.github/workflows/issue-open-check.yml

@@ -0,0 +1,34 @@
+name: Issue Open Check
+
+on:
+  issues:
+    types: [opened]
+
+jobs:
+  issue-open-check:
+    permissions:
+      issues: write
+    runs-on: ubuntu-latest
+    steps:
+      - name: check issue title
+        id: check-issue
+        uses: actions/github-script@v6
+        with:
+          script: |
+            const title = context.payload.issue.title;
+            const titleSplit = title.split(/\s+/).map(e => e.toLowerCase());
+            const keywords = ['api', 'treesitter', 'ui', 'lsp', 'doc'];
+            var match = new Set();
+            for(const keyword of keywords) {
+              if(titleSplit.includes(keyword)) {
+                match.add(keyword)
+              }
+            }
+            if(match.size !== 0){
+              github.rest.issues.addLabels({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                issue_number: context.issue.number,
+                labels: Array.from(match)
+              })
+            }