fix: export tree adapter types as namespace to support TS4.x

[43081j]

Exports the tree adapter types as a namespace, individually. This reintroduces typescript 4.x support, which we accidentally broke in a non-breaking release.

Fixes #1299

Before we merge this I need to double check it really does fix the problem. I tried building it with 4.x and it works but I need to check the types are still the same

[43081j]

seems to fix it so I'm going ahead and merging this 👀

[wooorm]

If you want a review, I’d recommend keeping PRs open some non-weekend days too. I personally try not to work on the weekends. Some places (rust, node, unifiedjs) use a lazy consensus time of 72 hours.
That being said, if you don’t believe a review is needed, I’m fine with you merging immediately

[43081j]

i wasn't planning on waiting for a review for this one unless someone happened to be around

i already tested that the types work as expected and discussed it somewhat on the TS discord, so figured its probably all good

will keep it in mind though, ive lost track of days a lot when travelling lately, my bad.