converted to unity package manager package.

[HoomanJCode]

Hello, now we have a unity package that can be imported from the package manager.

1. open package manager
2. add from git
   
3. import sample
   

problems: this will break your ".unitypackage " production pipeline.
benefits: you can add, use and update easily.
todos:

• set required unity version.
• edit Readme for installation help.
• add changelog and documentation links to the package manifest.

[HoomanJCode]

not change any code or script.
I have removed TMP imports and moved files to a package structure. user will prompt if import samples and want to use.

[pnarimani]

Hi, Thanks for the PR.

Since this change moves a lot of files around, it creates difficulties for people who are already using the package and are trying to upgrade.

It's better to simply add package.json file to RTLTMPro folder and use UPM's subfolder feature:
SubFolders