docs: restored page on roles in security, executed other touchups, and… (#11978)

* Restored docs page on roles in security, executed other touchups, and renamed docs readme.txt to readme.md

* missed a url anchor on the security page

* fixed licensing issue and limited char width to 80

* fixed licensing issue and limited char width to 80

* whitespace experiments

* removed 2 periods

* staging whitespace

* addressed Robs feedback

* implemented robs second round of feedback on public_role_like

docs/README.md

@@ -0,0 +1,67 @@
+<!--
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements.  See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership.  The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License.  You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied.  See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+Here's the source to the documentation hosted at
+<a href="https://superset.apache.org">superset.apache.org</a>
+
+The site runs on the Gatsby framework and uses docz for it's
+`Documentation` subsection.
+
+
+## Getting Started
+
+```bash
+cd docs/
+npm install
+npm run start
+# navigate to localhost:8000`
+```
+
+## To Publish
+
+To publish, the static site that Gatsby generates needs to be pushed
+to the `asf-site` branch on the
+[apache/incubator-superset-site](https://github.com/apache/incubator-superset-site/)
+repository. No need to PR here, simply `git push`.
+
+```bash
+# Get in the docs/ folder in the main repo
+cd ~/repos/incubator-superset/docs
+# have Gatsby build the static website, this puts in under `docs/public`
+npm run build
+
+# go to the docs repo
+cd ~/repos/incubator-superset-site
+# checkout the proper branch
+git checkout asf-site
+
+# BE CAREFUL WITH THIS COMMAND
+# wipe the content of the repo
+rm -rf *
+
+# copy the static site here
+cp -r ~/repos/incubator-superset/docs/public/ ./
+
+# git push
+git add .
+git commit -m "relevant commit msg"
+git push origin asf-site
+
+# SUCCESS - it should take minutes to take effect on superset.apache.org
+```