Add README instructions for serving the docs locally (#287)

* Add README instructions for serving the docs locally

* Rename readme.md to README.md

* Add a title

Co-authored-by: TheFrenchGhosty <47571719+TheFrenchGhosty@users.noreply.github.com>

README.md

@@ -0,0 +1,17 @@
+# The Invidious documentation
+
+# Running the documentation locally for development purposes
+
+## Local `mkdocs-material` installation
+
+```bash
+# You might want to create a virtualenv first
+pip install mkdocs-material
+mkdocs-material serve
+```
+
+## With docker
+
+```bash
+docker run --rm -it -p 8000:8000 -v ${PWD}:/docs squidfunk/mkdocs-material:latest
+```