Add support for Search and Replace done only for text outside of xhtml elements

[kevinhendricks]

There is a need to more easily support Search and Replace done only for text outside of xhtml elements.
I am thinking of a Text Only checkbox added to search and replace that ignores/removes all element tags/attributes from the material to run search/replace on.

This can actually be done in a limited fashion using regex to restrict the search to being outside of an element "<" to ">" range. But something easier to most users would be nice.

[kevinhendricks]

See this post for example of how to do this via regular expressions until this gets fixed:

https://www.mobileread.com/forums/showpost.php?p=4099971&postcount=169

[UnrulyNatives]

@kevinhendricks
Thank you for your support in adding this feature. It is clearly needed, as there were several attempts to introduce it: #618.
This is a working regex snipped which I got from someone at Stack Overflow: <[^<>]*>(*SKIP)(*F)
https://stackoverflow.com/questions/67846197/sigil-editor-regex-string-to-look-for-a-hyphen-character-in-text-but-not-htm/67858204#67858204

[kevinhendricks]

Both seem to work. Now you can save it as a Saved Search and call it up easily whenever you want.