Cleanup .eslintignore file in addon blueprint

[SergeAstapov]

Follow up to #73

[SergeAstapov]

cc @bertdeblock

[bertdeblock]

I think these could be removed as well:

• /vendor/ - Normally, shouldn't be needed anymore for modern apps and addons, a PR was merged in Ember CLI to remove the folder from the blueprints: [ENHANCEMENT] Remove vendor folder from app blueprint ember-cli/ember-cli#10050
• /node_modules/ - ESLint ignores /node_modules/ by default - This is mentioned here in the docs: https://eslint.org/docs/latest/user-guide/configuring/ignoring-code#the-eslintignore-file
• .eslintcache - ESLint ignores dot files by default, I also think ESLint doesn't pick up non JS files by default? Would also be weird if it would try to lint its own cache file 😬

[SergeAstapov]

makes sense, thanks for recommendations @bertdeblock! updated PR

[simonihmig]

Thanks @SergeAstapov!