`data-*` string mutations are broken

[Archmonger]

data_bs_toggle="..." is rendered as data-bs_toggle="..." (idom==1.0.0a2).

Originally posted by @numpde in https://github.com/idom-team/idom/discussions/903#discussioncomment-4862494

[Archmonger]

Closing due to new design direction for 1.0.0