Add exports of `one`, `all` helpers

[ignatiusreza]

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

re-export all and one from index.js, closes #53

originally I thought we could also re-export revert, and wrap, but looking at the implementation, it looks like those 2 are quite specialized for processing only some type of node, so I refrain from re-exporting them..

[wooorm]

Released, thanks @ignatiusreza!