Add .eslintignore to ignore linked gitlab-ui

Add .eslintignore to ignore linked gitlab-ui

This helps with local development when making changes to gitlab-ui and you want to see them reflected in Pajamas locally.

Added from comments for more visibility:

node_modules are ignored by default. This is to explicitly fix eslint failing when using yarn link to reference a local instance of gitlab-ui. The globs are there because everyone will have gitlab-ui installed under a different path.