behavior click: Support matching text

[PromyLOPh]

Matching CSS selectors is becoming increasingly difficult, as big sites usually obfuscate their CSS class names/use random names. Matching text could provide a way out. Additionally matching text could be used as a heuristic: Look for “load more”, if it’s clickable and at the end of a container (say, <div>), click it, revert (i.e. reject navigation request) if necessary.