jcforest

@twschiller @fregante I created PR here and still need to polish more however I'd like to hear feedback from you about this PR.

@twschiller When do we inject pageScript? The interesting point is the selector created from `safeCssSelector` function passes `requreSingleElement` validation [here](https://github.com/pixiebrix/pixiebrix-extension/blob/dadda478584d06d2015c7bbc3d98b42da07b035b/src/nativeEditor/selector.ts#L197) but it doesn't find the element with same selector in...

@jcforest To recap our call, here's what we need for this PR: - [x] Run selector generation from the content script instead of the page script when framework is not...

@twschiller I updated PR as we discussed.