Add exports of `defaultHandlers`, `all`, `one`

[JounQin]

Initial checklist

• [x] I read the support docs
• [x] I read the contributing guide
• [x] I agree to follow the code of conduct
• [x] I searched issues and couldn’t find anything (or linked relevant results below)
• [x] If applicable, I’ve added docs and tests

Description of changes

Just like https://github.com/rehypejs/rehype-remark/pull/9

[codecov-commenter]

Codecov Report

Merging #23 (e72963a) into main (e071630) will not change coverage. The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main       #23   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            2         2           
  Lines           79        81    +2     
=========================================
+ Hits            79        81    +2     

Impacted Files	Coverage Δ
index.js	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update e071630...e72963a. Read the comment docs.

[github-actions[bot]]

Hi! This was closed. Team: If this was merged, please describe when this is likely to be released. Otherwise, please add one of the no/* labels.

[wooorm]

Thanks, released!