Add workflows

Author: MattyTheHacker

.github/workflows/pr-auto-label.yml

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+name: "Automatically mark PRs to sync"
+
+on:
+  pull_request:
+    types:
+      - opened
+
+jobs:
+  labeler:
+    if: github.event.pull_request.user.type != 'Bot'
+    permissions:
+      pull-requests: write
+
+    runs-on: ubuntu-latest
+    steps:
+      - name: Add "sync" label to PR
+        run: gh pr edit "$PR_URL" --add-label sync --repo "$PR_REPO"
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          PR_URL: ${{ github.event.pull_request.html_url }}
+          PR_REPO: ${{ github.repository }}
+
+      - name: Comment on PR to explain sync label
+        run: gh pr comment "$PR_URL" --body "This pull request has been marked to **automatically sync** to its base branch. You can **disable** this behavior by removing the `sync` label." --repo "$PR_REPO"
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          PR_URL: ${{ github.event.pull_request.html_url }}
+          PR_REPO: ${{ github.repository }}

.github/workflows/pr-auto-merge.yml

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+name: "Automatically enable auto-merge on PRs"
+
+on:
+  pull_request_target:
+    types:
+      - opened
+      - ready_for_review
+    branches:
+      - main
+
+jobs:
+  enable-automerge:
+    if: github.event.pull_request.draft == false
+    permissions:
+      pull-requests: write
+
+    runs-on: ubuntu-latest
+    steps:
+      - name: Enable auto-merge for the PR
+        run: gh pr merge "$PR_URL" --auto --squash
+        env:
+          GH_TOKEN: ${{ secrets.PR_AUTO_UPDATE_TOKEN }}
+          PR_URL: ${{ github.event.pull_request.html_url }}

.github/workflows/pr-auto-update.yml

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+name: pr-auto-update
+on:
+  push: {}
+
+jobs:
+  pr-auto-update:
+    name: Automatic PR Updater
+    runs-on: ubuntu-latest
+    permissions: 
+      pull-requests: write
+      contents: write
+    steps:
+      - name: Generate Access Token
+        uses: actions/create-github-app-token@v2
+        id: generate-token
+        with:
+          app-id: ${{ vars.PR_AUTO_UPDATE_CLIENT_ID }}
+          private-key: ${{ secrets.PR_AUTO_UPDATE_PRIVATE_KEY }}
+
+      - uses: CSSUoB/pr-auto-updater@v2.3.1
+        env:
+          GITHUB_TOKEN: ${{ steps.generate-token.outputs.token }}
+          PR_FILTER: 'labelled'
+          PR_LABELS: 'sync'
+          MERGE_CONFLICT_ACTION: 'label'
+          MERGE_CONFLICT_LABEL: 'conflict'