chore: create GitHub action to update the canary branch

.github/workflows/update-canary.yml

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+name: Update canary branch
+
+on:
+  schedule:
+    - cron: '0 6 * * *'
+  workflow_dispatch:
+
+jobs:
+  updateCanary:
+    name: Update the canary branch
+    if: github.repository == 'nodejs/node-v8' || github.event_name == 'workflow_dispatch'
+    runs-on: ubuntu-latest
+    steps:
+      - name: Clone node-v8
+        uses: actions/checkout@v2
+        with:
+          path: node-v8
+          token: ${{ secrets.CANARY_UPDATE }}
+
+      - name: Install Node.js
+        uses: actions/setup-node@v2
+        with:
+          node-version: 14.x
+
+      - name: Install dependencies
+        run: npm install -g node-core-utils@latest
+
+      - name: Cache V8 clone
+        uses: actions/cache@v2
+        with:
+          path: v8
+          key: v8-clone
+
+      - name: Execute the update script
+        run: ./node-v8/tools/update-canary.sh
+
+      - name: Notify Slack on failure
+        if: ${{ failure() }}
+        run: |
+          ACTIONS_URL="${GITHUB_SERVER_URL}/${GITHUB_REPOSITORY}/actions/runs/${GITHUB_RUN_ID}?check_suite_focus=true"
+          SLACK_PAYLOAD="{\"username\": \"canary_bot\", \"text\": \"*Canary update failed!*\n\nRun: ${ACTIONS_URL}\", \"icon_emoji\": \":bell:\"}"
+          curl -X POST --data-urlencode "payload=${SLACK_PAYLOAD}" ${{ secrets.SLACK_WEBHOOK }}

README.md

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+# Node.js V8 canary
+
+This is an automatically updated **experimental** version of [Node.js][] with
+the `lkgr` (last known good revision) of V8.
+
+The daily builds of this repo can be found at [`v8-canary`][].
+
+**Do not use this in production!**
+
+This repository is not owned by `@nodejs/v8`, but they might be able to help
+with issues.
+
+This project is bound by a [Code of Conduct][].
+
+[Code of Conduct]: https://github.com/nodejs/admin/blob/HEAD/CODE_OF_CONDUCT.md
+[Node.js]: https://github.com/nodejs/node
+[`v8-canary`]: https://nodejs.org/download/v8-canary/

tools/update-canary.sh

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+#!/usr/bin/env bash
+
+set -ex
+
+cd node-v8
+
+git remote add upstream https://github.com/nodejs/node.git
+git fetch upstream master
+git fetch upstream canary-base
+
+git config user.name "Node.js GitHub Bot"
+git config user.email github-bot@iojs.org
+
+git reset --hard upstream/master
+
+# Update V8 to the lkgr branch
+git-node v8 major --branch=lkgr --base-dir="$GITHUB_WORKSPACE"
+
+# Cherry-pick the floating V8 patches Node.js maintains on master.
+# Canary-base is the last good version of canary, and is manually updated with any V8 patches or backports.
+git cherry-pick `git log upstream/canary-base -1 --format=format:%H --grep "src: update NODE_MODULE_VERSION"`...upstream/canary-base
+
+# Verify that Node.js can be compiled and executed
+python3 ./configure
+make -j $(getconf _NPROCESSORS_ONLN) V=
+out/Release/node test/parallel/test-process-versions.js
+
+# Force-push to the canary branch.
+git push --force origin HEAD:canary