Consider argsIgnorePattern for no-unused-vars rule

[joshuacurtiss]

There are instances, such as implementing/extending a class with a function that has an argument that your implementation won't use, which will trigger the no-unused-vars eslint rule.

Typically, we may just disable no-unused-vars when this occurs, such as here:
https://github.com/silvermine/service-web/blob/77db28f0/service-web-core/src/model/Web.ts#L48

In these cases, we nearly always use a prepended underscore by convention to signify the arg is unused, but still have to disable the rule.

If we modify the rule like this:

'no-unused-vars': [ 'error', { 'argsIgnorePattern': '^_' } ],

Then the convention we are already using will automatically be ignored by the rule and we'll no longer have to explicitly disable the rule with an eslint-disable-line comment.

diff --git a/index.js b/index.js
index f8b966b..25051e9 100644
--- a/index.js
+++ b/index.js
@@ -140,7 +140,7 @@ module.exports = {
       'no-shadow-restricted-names': 'error',
       'no-undef': 'error',
       'no-undef-init': 'error',
-      'no-unused-vars': 'error',
+      'no-unused-vars': [ 'error', { 'argsIgnorePattern': '^_' } ],
       'no-use-before-define': [ 'error', { 'functions': false } ],
 
       'callback-return': [ 'error', [ 'callback', 'cb', 'next', 'done' ] ],
@@ -284,7 +284,7 @@ module.exports = {
             // The standard ESLint `no-unused-vars' rule will throw false positives with
             // class properties in TypeScript. The TypeScript-specific rule fixes this.
             'no-unused-vars': 'off',
-            '@typescript-eslint/no-unused-vars': 'error',
+            '@typescript-eslint/no-unused-vars': [ 'error', { 'argsIgnorePattern': '^_' } ],
             // For TypeScript code, `const`/`let` should be used exclusively
             'no-var': 'error',
             // new-cap throws errors with property decorators

[jthomerson]

I like it. @onebytegone thoughts?