Add Props Bot.

This adds a GitHub Actions workflow that runs the Props Bot.

.github/workflows/props-bot.yml

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+name: Props Bot
+
+on:
+  # This event runs anytime a PR is (re)opened, updated, or labeled.
+  # The logic below will look for
+  pull_request:
+    types:
+      - opened
+      - synchronize
+      - reopened
+      - labeled
+  # This event runs anytime a comment is added or deleted.
+  # You cannot filter this event to happen for PR comments only.
+  # However, the logic below does short-circuit the workflow for issues.
+  issue_comment:
+    type:
+      - created
+      - deleted
+  # This event will run everytime a new PR review is created.
+  pull_request_review:
+    types:
+      - submitted
+  # This event runs anytime a PR review comment is added or deleted.
+  pull_request_review_comment:
+    types:
+      - created
+      - deleted
+
+# Cancels all previous workflow runs for pull requests that have not completed.
+concurrency:
+  # The concurrency group contains the workflow name and the branch name for pull requests
+  # or the commit hash for any other events.
+  group: ${{ github.workflow }}-${{ contains( fromJSON( '["pull_request", "pull_request_review", "pull_request_review_comment"]' ), github.event_name ) && github.head_ref || github.sha }}
+  cancel-in-progress: true
+
+# Disable permissions for all available scopes by default.
+# Any needed permissions should be configured at the job level.
+permissions: {}
+
+jobs:
+  # Compiles a list of props for a pull request.
+  #
+  # Performs the following steps:
+  # - Collects a list of contributor props and leaves a comment.
+  # - Removes the props-bot label, if necessary.
+  props-bot:
+    name: Generate a list of props
+    runs-on: ubuntu-latest
+    permissions:
+      # The action needs permission `write` permission for PRs in order to add a comment.
+      pull-requests: write
+      contents: read
+    timeout-minutes: 20
+    if: |
+      contains( fromJSON( '["pull_request_review", "pull_request_review_comment"]' ), github.event_name ) ||
+      ( github.event_name == 'issue_comment' && github.event.issue.pull_request ) ||
+      github.event.action != 'labeled' ||
+      'props-bot' == github.event.label.name
+
+    steps:
+      - name: Gather a list of contributors
+        uses: WordPress/props-bot-action@trunk
+
+      - name: Remove the props-bot label
+        uses: actions/github-script@60a0d83039c74a4aee543508d2ffcb1c3799cdea # v7.0.1
+        if: ${{ github.event.action == 'labeled' && 'props-bot' == github.event.label.name }}
+        with:
+          retries: 2
+          retry-exempt-status-codes: 418
+          script: |
+            github.rest.issues.removeLabel({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: '${{ github.event.number }}',
+              name: 'props-bot'
+            });