docs: move to docusaurus (#1984)

* new site start

* ci: test docusaurus

* we use npm

* Update site_tests.yml

* Update site_tests.yml

* Update site_tests.yml

* do not ignore package.json

* Update package-lock.json

* Create deploy.yml

* Update docusaurus.config.js

* update authors

* Update docusaurus.config.js

* Update deploy.yml

* remove blog posts

* Update README.md

* delete old docs

* Update .gitignore

* delete template images

* Create 2022-02-03-welcome.md

.github/workflows/site_tests.yml

@@ -0,0 +1,23 @@
+name: Test Docusaurus build
+
+on:
+  pull_request:
+    paths:
+      - "docs/**"
+
+jobs:
+  test-deploy:
+    name: Test deployment
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-node@v2
+        with:
+          node-version: 14.x
+          cache: npm
+          cache-dependency-path: site/package-lock.json
+      - name: Test build
+        working-directory: site
+        run: |
+          npm ci
+          npm run build