fix: create parent dirs for dist folder if don't exist

[ZibanPirate]

fixes #826

there two more places where we still use create_dir instead of create_dir_all here. maybe we want to fix those as well? and ideally have a linting rule to always use create_dir_all instead of create_dir as we already use a mix of both accross the repo.

steps to reproduce

• build the project. cargo build
• navigate to examples/yew
• modify the dist value in examples/yew/Trunk.toml to something like dist = "dist/sub".
• run the locally built version of trunk on this directory: ../../target/debug/trunk build

on main you should get the error that parent dir doesn't exists.
on this branch, the parent dir should be created and the build passes.

[ctron]

Thanks for the PR. Makes perfect sense.

I think this could even be improved as create_dir_all will handle a "does already exists" case.

If there are similar cases like that, it would be great to fix them as well in the same PR if you can find the time.