Migrate from Yarn to Bun

https://bun.sh/
https://github.com/oven-sh/setup-bun

Author: simon04

.github/workflows/node-ci.yml

@@ -7,13 +7,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
-      - uses: actions/setup-node@v3
-        with:
-          node-version: '20'
-      - run: corepack enable
-      - run: yarn install
-      - run: yarn test
-      - run: yarn build
+      - uses: oven-sh/setup-bun@v2
+      - run: bun install --frozen-lockfile
+      - run: bun run test
+      - run: bun run build
       - uses: peaceiris/actions-gh-pages@v3
         if: github.event_name == 'push' && github.ref == 'refs/heads/master'
         with:

.yarnrc.yml

@@ -1,7 +1,6 @@
 {
   "name": "tyrolean-map",
   "version": "1.0.0",
-  "packageManager": "yarn@4.9.2",
   "description": "Frontend to various maps published by Land Tirol and South Tyrol as Open Government Data",
   "main": "app.ts",
   "scripts": {