Auto-add 'cody' label to issues for filtering in Linear (#3474)

The `cody` label will allow constructing unified Views inside Linear for Cody-related
issues filed on different repos, such as the Sourcegraph monorepo, this repo, and
the sourcegraph/customer repo.

.github/labeler.yml

@@ -0,0 +1,2 @@
+cody:
+    - '/.*/'

.github/workflows/labeler.yml

@@ -0,0 +1,18 @@
+name: "Issue Labeler"
+on:
+  issues:
+    types: [opened, edited]
+
+permissions:
+  issues: write
+  contents: read
+
+jobs:
+  triage:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: github/issue-labeler@v3.4
+      with:
+        configuration-path: .github/labeler.yml
+        enable-versioned-regex: 0
+        repo-token: ${{ github.token }}