markdown support in descriptions

We should at least be able to render markdown from descriptions.

Does anyone actually write markdown on phone apps? Should we support that on publish/channel description inputs?

Start by locating the Android screens and input/rendering paths for publish and channel descriptions; the issue names no files or tests. Clarify which description fields should accept Markdown, then define done as consistent Markdown rendering in the selected fields and verify it through the relevant app flows.

Written by the indexing model from the issue text.