fix: add rootDir to tsconfig.json

[aeons]

The most recently released version (0.2.1) has output files nested in lib/src (see https://npmx.dev/package-code/@e18e/web-features-codemods/v/0.2.1/lib%2Fsrc%2Fmain.js), which breaks imports from the package.

Building also gives this warning currently:

❯ npm run build

> @e18e/web-features-codemods@0.0.1 build
> tsgo

tsconfig.json:3:5 - error TS5011: The common source directory of 'tsconfig.json' is './src'. The 'rootDir' setting must be explicitly set to this or another path to adjust your output's file layout.
  Visit https://aka.ms/ts6 for migration information.

3     "outDir": "./lib",
      ~~~~~~~~


Found 1 error in tsconfig.json:3

This PR sets the rootDir to ./src, which fixes the error and the output.

That was a lot of text for a one line change :D

[aeons]

FYI @43081j, the latest release being broken also breaks the e18e cli (when used via npx or equivalent at least).

[43081j]

I'm away right now but will cut a release soon as I'm at a laptop 👍 it is a shame ci didn't catch this