Document squash and squash- commands

Author: kellda

homu/html/index.html

@@ -66,6 +66,8 @@ <h3>Commands</h3>
                 <li><code>rollup</code>: Mark the PR as likely to merge without issue, short for <code>rollup=always</code></li>
                 <li><code>rollup-</code>: Unmark the PR as <code>rollup</code>.</li>
                 <li><code>rollup=maybe|always|iffy|never</code>: Mark the PR as "always", "maybe", "iffy", and "never" rollup-able.</li>
+                <li><code>squash</code>: Squash all commits into one just before performing the merge.</li>
+                <li><code>squash-</code>: Do not squash commits before merging.</li>
                 <li><code>retry</code>: Signal that the PR is not bad, and should be retried by buildbot.</li>
                 <li><code>try</code>: Request that the PR be tested by buildbot, without accepting it.</li>
                 <li><code>force</code>: Stop all the builds on the configured builders, and proceed to the next PR.</li>