doc: Add LGTM.com code quality badges

Add LGTM.com code quality badges as an incentive for contrinbutors to care about code quality

Signed-off-by: Xavier RENE-CORAIL <[email protected]>

Author: xcorail

README.md

@@ -3,6 +3,8 @@
 [![Dependency Status](https://david-dm.org/db-migrate/node-db-migrate.svg)](https://david-dm.org/db-migrate/node-db-migrate)
 [![devDependency Status](https://david-dm.org/db-migrate/node-db-migrate/dev-status.svg)](https://david-dm.org/db-migrate/node-db-migrate#info=devDependencies)
 [![Documentation Status](https://readthedocs.org/projects/db-migrate/badge/?version=latest)](https://readthedocs.org/projects/db-migrate/?badge=latest)
+[![Code Quality: Javascript](https://img.shields.io/lgtm/grade/javascript/g/db-migrate/node-db-migrate.svg?logo=lgtm&logoWidth=18)](https://lgtm.com/projects/g/db-migrate/node-db-migrate/context:javascript)
+[![Total Alerts](https://img.shields.io/lgtm/alerts/g/db-migrate/node-db-migrate.svg?logo=lgtm&logoWidth=18)](https://lgtm.com/projects/g/db-migrate/node-db-migrate/alerts)
 
 # db-migrate