Makes workflow-ui/compose/README.md informative.

`README.md` is now the permanent home of the [blog post](https://developer.squareup.com/blog/jetpack-compose-support-in-workflow/) that described in depth how this stuff would work, so that we can keep it up to date.

Closes #458

Author: zach-klippenstein

.markdownlint.rb

@@ -6,8 +6,8 @@
 # Need to explicitly run all rules, so the per-rule configs below aren't used as an allowlist.
 all
 
-# Increase default line length from 80 to 100.
-rule 'MD013', :line_length => 100, :code_blocks => false, :tables => false
+# We don't care about line length, because it prevents us from pasting in text from sane tools.
+exclude_rule 'MD013'
 
 # Enable inline HTML.
 exclude_rule 'MD033'