feat(client): focus and xpath dom extenders

[blakebyrnes]

This PR adds 3 dom extenders:

• $hasFocus - is a field focused
• $xpathSelector(path, ordered = false) - runs a singleNode xpath selector
• $xpathSelectorAll(path, ordered = false) - runs multiNode xpath selector

Also fixes an issue where interact wasn't working on xpath elements due to not evaluating the parameters to the xpath