PHP 8 Support (#164)

* Update composer.json

* Update .travis.yml

remove invideoPromotion (#157)

fix: part param doesn't accept space anymore (#152)

All the lib queries stopped to work for me today, debbuging I see that without the space in `part` parameter, everything works normally again.

ValidYoutubeVideo Rule (#145)

* ValidYoutubeVideo Rule

* Removed extra accidental line

* Update ValidYoutubeVideo.php

* Delete .gitignore

* Revert "Delete .gitignore"

This reverts commit 0e78d94.

* Only request video id

* Restore .gitignore to master original

* Revert "Restore .gitignore to master original"

This reverts commit ff7eced.

* Update .gitignore

* Update README.md

Update README.md

Merge pull request #96 from bzbislawski/no-config-option

Fixes #94 - No config option

Merge pull request #69 from v1shky/master

Added getCategories method

Merge pull request #67 from bzbislawski/php5

Update readme

Merge pull request #66 from bzbislawski/master

Upgrade to php7 and psr-4

Merge pull request #63 from hoyama/modify

Support comma-separated list of IDs in getChannelbyId