Enable no-extra-semi

The rule:
https://eslint.org/docs/rules/no-extra-semi
disallows unnecessary semicolons, e.g. it forbids the following:
```js
var x = 5;;

function foo() {
    // code
};
```

In jQuery we usually don't add a semicolon at the end of function declarations
but I found a few cases where we do, creating an inconsistency.

Author: mgol

.eslintrc.json

@@ -112,6 +112,7 @@
 				"after": true
 			}
 		],
+		"no-extra-semi": "error",
 		"space-infix-ops": "error",
 		"eol-last": "error",
 		"lines-around-comment": [