Host solo docs directly at docs.solokeys.{dev,io}

docs/documenting.md

@@ -0,0 +1,11 @@
+Documentation of the `master` branch is deployed to Netlify automatically.
+
+To host or develop locally:
+
+```
+pip install mkdocs mkdocs-material markdown-include
+```
+
+`mkdocs serve` and visit [localhost:8000](http://localhost:8000).
+
+The file `runtime.txt` is necessary to tell Netlify to use Python3.