Version 7.0.0

Changes:

• ⚠️ lint-readme has been removed (#60)
• ⚠️ test now uses oletus and c8 rather than mocha and nyc (#64)
• lint-package-json no longer uses spdx-expression-parse to validate license field (#66)
• doctest dependency upgraded from 0.20.x to 0.21.x (#62)
• sanctuary-style dependency upgraded from 7.0.x to 8.0.x (#68)