Add the wiki, Quality and Release workflows

Add a wiki/ folder with a .publish marker for the shared Publish wiki
workflow, a Quality workflow (shellcheck and shfmt through the shared
reusable workflow) and a manual Release workflow that builds the release
page from CHANGELOG.md.

Set switch_case_indent for *.sh in .editorconfig so shfmt accepts the
existing case layout.

wiki/_Sidebar.md

@@ -0,0 +1,4 @@
+- [Home](Home)
+- [Getting started](Getting-started)
+- [SSH and tokens](SSH-and-tokens)
+- [Troubleshooting](Troubleshooting)