Resolve tailwindcss relative to the file being processed

[thecrypticace]

Breaking change

tailwindcss is now resolved relative to each processed file

Loading the tailwindcss version relative to each processed file produces more correct behavior for monorepos where tailwindcss may not be installed at the project root but instead in a subdirectory. Because of this projects with multiple Tailwind CSS versions in the same repo are also more likely to work than before.

Automatically loaded v3 configs are resolved relative to each processed file

Similar to the above, the same happens when we automatically locate your v3-style config files. Previously these were always searched for relative to the Prettier config — this often meant the file needed to be in the project root. This is no longer the case which should improve support for monorepos with multiple configs using Tailwind CSS v3.

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This ended up turning into a complete rework of the module and config loading. There's definitely going to be some different perf characteristics because some things are loaded relative to an input file now but it's hopefully minimal.

Will need to do lots of perf testing on a large codebase — esp with lots of embedded languages/expressions (e.g. large Vue files).

• Needs implementation tests
• Needs manual performance testing

Closes #243 (since the implementation is now entirely different but does the same thing)
Fixes #340
Closes #361
Closes #363
Closes #369

[RobinMalfait]

Looking good, a few small questions/suggestions.

The src/config.ts file reads very nicely right now.

I think technically this change could be a breaking change, but for people with simple setups looking for tailwindcss from the config or input file shouldn't result in any differences. But for people with a more complex (monorepo) setup it should solve locating tailwindcss correctly.

Running into some issues with this PR, let's discuss this on Tuple later 👍