Filesystem.php had a typo in comment

Feel free to merge this or not, but I noticed a typo in the comment. Not sure this really requires a full pull request though. It was only missing the letter 'y' in directory.
Removed trailing whitespace
Update phpdocs for better chaining

Following the PSR-5 Proposal, chained methods should use `return $this`.
New instances should use `return static`. This way, when classes are
extended, they refer to the correct class.
Replace more static return types
Add path option to RemindersControllerCommand
Fix docblock
[4.2] Router Docblock Fix
Merge pull request #5303 from KennedyTedesco/patch-1

[4.2] Router Docblock Fix
Merge pull request #5297 from GrahamCampbell/4.2-whitespace

[4.2] Removed Trailing Whitespace
Merge pull request #5299 from barryvdh/return-this

[PHPDoc] Update phpdocs for better chaining (return $this)
Merge pull request #5301 from antonioribeiro/addPathOptionToRemindersControllerCommand

Add path option to RemindersControllerCommand
Working on code.
Merge pull request #5294 from ikari7789/patch-1

Filesystem.php had a typo in comment
Spacing.