Update README.md to fix cosmiconfig reference

[joshmeads]

Fix the cosmiconfig docs

Description

As noted in #192 .lockfile-lint.js is invalid. .lockfile-lintrc.js should be a valid Cosmiconfig with the default setup which you appear to be using.

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Related Issue

#192

Motivation and Context

Fixes invalid docs

How Has This Been Tested?

Screenshots (if appropriate):

Checklist:

• [x] I have updated the documentation (if required).
• [ ] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.
• [ ] All new and existing tests passed.
• [ ] I added a picture of a cute animal cause it's fun