[WIP] Added PHPDoc type hints, encoding issues, errors reported by IDE and PHPStan

[StudioMaX]

• Fixed charset in changelog.txt
• Added .editorconfig to not mix-up different new line separators and spacing created by different editors
• PHPDoc with type hints for the most methods
• Fixed some issues reported by IDE and PHPStan

[StudioMaX]

@JamesHeinrich Travis says (https://travis-ci.org/JamesHeinrich/getID3) that it was disabled on this project, why? I found a lot of errors after implementing the PHPDoc type hinting and launching the PHPStan analyzer, and most of them probably can be fixed with your help. Can you enable it back, please?

[JamesHeinrich]

@StudioMaX: Travis CI was emailing me daily about something failing, and I didn't know who signed me up for it, so I turned it off. I've re-enabled it for you.

For example, it blandly says Build #48 is still failing
I have no idea what's failing or why, nor how to fix it. Since you seem to know something about it please fix it :)

[JamesHeinrich]

@StudioMaX: Packagist.org also emailed me as follows, since I assume it's related to whatever you're doing perhaps you can address that issue as well:

The james-heinrich/getid3 package of which you are a maintainer has
failed to update due to invalid data contained in your composer.json.
Please address this as soon as possible since the package stopped updating.

It is recommended that you use `composer validate` to check for errors when you
change your composer.json.

Below is the full update log which should highlight errors as
"Skipped branch ...":

[Composer\Repository\InvalidRepositoryException]: Some branches contained invalid data and were discarded, it is advised to review the log and fix any issues present in branches

Reading composer.json of james-heinrich/getid3 (v1.9.15)
Importing tag v1.9.15 (1.9.15.0)
Reading composer.json of james-heinrich/getid3 (v1.9.14)
Importing tag v1.9.14 (1.9.14.0)
Reading composer.json of james-heinrich/getid3 (v1.9.13)
Importing tag v1.9.13 (1.9.13.0)
Reading composer.json of james-heinrich/getid3 (v1.9.12)
Importing tag v1.9.12 (1.9.12.0)
Reading composer.json of james-heinrich/getid3 (v1.9.11)
Importing tag v1.9.11 (1.9.11.0)
Reading composer.json of james-heinrich/getid3 (v1.9.10)
Importing tag v1.9.10 (1.9.10.0)
Reading composer.json of james-heinrich/getid3 (v1.9.9)
Importing tag v1.9.9 (1.9.9.0)
Reading composer.json of james-heinrich/getid3 (v1.9.8)
Importing tag v1.9.8 (1.9.8.0)
Reading composer.json of james-heinrich/getid3 (1.9.7)
Skipped tag 1.9.7, no composer file
Reading composer.json of james-heinrich/getid3 (master)
Importing branch master (dev-master)
Skipped branch master, Invalid package information:
License "GPL" is not a valid SPDX license identifier, see https://spdx.org/licenses/ if you use an open license.
If the software is closed-source, you may use "proprietary" as license.

Reading composer.json of james-heinrich/getid3 (2.0)
Importing branch 2.0 (2.0.x-dev)
Skipped branch 2.0, Invalid package information:
License "GPL" is not a valid SPDX license identifier, see https://spdx.org/licenses/ if you use an open license.
If the software is closed-source, you may use "proprietary" as license.