Add ESLint Task

[MitchellMcKenna]

Q	A
Branch	master
Bug fix?	no
New feature?	yes
BC breaks?	no
Deprecations?	no
Documented?	yes
Fixed tickets	no

Add ESLint task for javascript code static analysis (code quality and coding style).

As a good amount of php projects also have some javascript frontend, it's handy to lint your JS during pre-commit as well.

Example task run:

$ git commit
GrumPHP detected a pre-commit command.
GrumPHP is sniffing your code!

Running task 1/4: phpcs... 
Running task 2/4: phpunit... 
Running task 3/4: phpstan... 
Running task 4/4: eslint... ✘

eslint
======

/resources/js/app.js
  23:1   error    Expected indentation of 4 spaces but found 8  indent

✖ 1 problem (1 error, 0 warnings)
  1 error potentially fixable with the `--fix` option.

You can fix all errors by running following commands:
'eslint' 'resources/js/app.js'  '--fix'
To skip commit checks, add -n or --no-verify flag to commit command

 I can fix some stuff automatically, do you want me to? (yes/no) [no]:
 > 

New Task Checklist:

• Are the dependencies added to the composer.json suggestions? (n/a)
• Is the doc/tasks.md file updated?
• Are the task parameters documented?
• Is the task registered in the tasks.yml file?
• Does the task contains phpunit tests?
• Is the configuration having logical allowed types?
• Does the task run in the correct context?
• Is the run() method readable?
• Is the run() method using the configuration correctly?
• Are all CI services returning green?

[veewee]

Thanks for the PR! It looks pretty good. I've added some small remarks.

[MitchellMcKenna]

Thanks for feedback. I will add fixer and update unit test.

Wow, you reviewed this like right away, impressive as I submitted it at like 2am my time, lol.

[veewee]

Thanks for your work. Really nice!