[FEATURE] Footnote Auto - Automatically use preceding h1 tag for text

[G-Ambatte]

Suggested in the subreddit recently was the idea that using an additional tag - for example, adding the auto class to the existing footnote element could trigger the use of the contents of the nearest preceding <h1></h1> tags.

I believe this functionality would need to be built in to the BrewRenderer, and in some ways may border on Brew Variables, in that it also replaces arbitrary value from the Brew text with a value that is defined elsewhere in that text.