Add .easignore as Ignore List filename

[spenserblack]

Description

This is probably on the edge of being popular enough. Without limiting the search to common keywords, there's a little over >300 results. Apologies if this isn't popular enough yet.

Checklist:

• I am adding a new extension filename to a language.
  • The new extension filename is used in hundreds of repositories on GitHub.com
    • Search results for each extension:
      • https://github.com/search?type=code&q=NOT+is%3Afork+path%3A%2F%28%5E%7C%5C%2F%29%5C.easignore%24%2F+node_modules
  • I have included a real-world usage sample for all extensions added in this PR:
    • Sample source(s):
      • https://github.com/bluesky-social/social-app/blob/3bab7f7540273a50501780b2f92076fbe41c8022/.easignore
    • Sample license(s):
      • MIT
  • I have included a change to the heuristics to distinguish my language from others using the same extension.