Bump @types/unist

[bberenberg]

@wooorm would you be ok with me making a PR to bump @types/unist to 3.x? It's a transitive dep into remark-mdx for me and I am trying to avoid conflicts.

[wooorm]

Hi! I’d like to but I held off because it’s breaking, and doesn’t really do much. @types/unist isn’t that big.

[bberenberg]

I agree, just trying to avoid conflicts on my end as parse-entities is the only one still using 2.x