vim: Add HTML tag support for #4503 (#8175)

a simple code for html tag support, I've only done the basics, and if
it's okay, I'll optimize and organize the code, and adapt other parts
like `is_multiline`, `always_expands_both_ways`, `target_visual_mode`,
etc

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Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>