[typeless-sample-bot]: Add an alternate tagging method to catch samples outside the sample browser

At the moment, the typeless-sample-bot only finds samples that have the `// [START foo]` tag in them. Unfortunately this also makes them show up in the sample browser, even when we don't have a `foo` ready for them (or do not intend to make one).

My intent is to add another regex to the typeless bot that it can look for to detect a sample it should munge into JS.