v7.0.0

Bump version to 7.0.0 for those who don't use custom .lints.json.

Changes:

• Add Bootlint

If you already have a .lints.json, in order to use Bootlint you
need to add it to your .lints.json, as in src/default.lints.json.

If you wish to disable some of the Bootlint's linters you can
create a .bootlintrc.json file in the root of your project with
an array of string linter IDs to disable, e. g.

["W001", "W002", "W003"]