markdownlint: allow break HTML

Github markdown only allows the `<br>` tag to be used in a table to
force a newline (there is otherwise no standard).  Allow this in the
markdownlint config.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I4d48352c678018d12aab3c1c9ec4c9e7eb1cbb42
1 file changed