Update README.md

Author: almarklein

README.md

@@ -1,2 +1,11 @@
 # pygfx.github.io
-pygfx home page
+
+The source of the pygfx-org home page.
+
+## Making changes
+
+The markdown files (and style files) can be edited and submitted via a PR. When the PR is merged, a GH Action builds and published the new site.
+
+## Local development
+
+The site is build using a little Python script in `makesite.py`. Just run it and then open `./output/index.html` in your browser to check the result.