chore: restore rumdl config comments

Signed-off-by: Gregor Zeitlinger <gregor.zeitlinger@grafana.com>

Author: zeitlinger

.github/config/.rumdl.toml

@@ -1,10 +1,13 @@
+# Converted from the repo's legacy markdownlint config.
 [global]
+# Disable the descriptive-link-text rule to preserve the old markdownlint policy.
 disable = ["MD059", "line-length", "no-inline-html", "MD041", "ul-style", "fenced-code-language"]
 
 [no-duplicate-heading]
 siblings-only = true
 
 [no-trailing-punctuation]
+# Allow exclamation points and question marks at the end of sentences.
 punctuation = ".,;:"
 
 [ol-prefix]