Editors generally look for configurations at the top level of a project. For ESLint, they also look for the specific binary in node_modules before defaulting to the system binary. Whilst you can override the location, generally it doesn't work well when switching between projects.
The custom in-tree libraries make setup of a system ESLint more difficult as well.
Therefore to make it simple for developers to pick up the ESLint integrations with Editors, by moving the package.json and associated node_modules to the top-level directory.
MozReview-Commit-ID: 1pQpd7hTQ61
--HG--
rename : tools/lint/eslint/npm-shrinkwrap.json => npm-shrinkwrap.json
rename : tools/lint/eslint/package.json => package.json
extra : rebase_source : 9d69d791f86b5c55b1fcd5f6449f0ab84e56b05c