docs(ci): Netlify ignore command to check branch

Add a separate ignore script that checks git changes but also
only deploys main and version branches to allow us to deploy
versioned docs.

docs/netlify-ignore-command.sh

@@ -0,0 +1,10 @@
+#!/bin/sh
+
+# We deploy main and version branches only
+if echo $HEAD | grep -E '^(main|v[[:digit:]]+\.([[:digit:]])+-branch)$'
+then
+  echo "Head '$HEAD' matches a deployed branch, checking for git changes."
+  git diff --quiet $CACHED_COMMIT_REF $COMMIT_REF . ../app/boards/
+else
+  exit 1
+fi

docs/netlify.toml

@@ -1,5 +1,5 @@
 [build]
-  ignore = "git diff --quiet $CACHED_COMMIT_REF $COMMIT_REF . ../app/boards/"
+  ignore = "bash ./netlify-ignore-command.sh"
 
 [[redirects]]
   from = "/community/discord/invite"