fix: Add build/.eslintrc.json to the files field in package.json

[pokutuna]

There is .eslintrc.json in build/ directory that is generated by tsc. This file is loaded from build/src/index.js but not listed in the files field.

This is already included in published tarballs.

$ curl -s https://registry.npmjs.org/gts/-/gts-2.0.2.tgz | tar tv | grep .eslintrc.json
   -rw-rw-r--  0 0      0        1407 10 26  1985 package/.eslintrc.json
   -rw-rw-r--  0 0      0        1663 10 26  1985 package/build/.eslintrc.json

This pr not only makes this package correct.
To add this file makes us able to use the head version from the GitHub repository, using yarn add -D gts@git+https://github.com/google/gts.git#master.

In installing from git dependency, the prepare script runs and compiles typescript files. But now it doesn't work, yarn copies files listed in the files to under node_modules from cache directory where this compiled.
(But failed on npm. I guess npm is failing to execute chmod to set permissions for bin files not compiled yet.)

[pokutuna]

Can someone please review this?
This change is tiny & based on the actual package.

src/index.ts will be placed at build/src/index.js after compiling, and loads build/.eslintrc.json

gts/src/index.ts

Line 17 in b3096fb

import * as cfg from '../.eslintrc.json';

I agree it's strange that files have 2 .eslintrc.json.

[JustinBeckwith]

Thanks for the fix and apologies for the delay. Agreed this is super weird, but looking at index.ts by golly you're right. I think this actually explains a few bugs I've seen 😆