[#56] Improve documentation for v0.2.0

[chshersh]

Resolves #56

I've improved the documentation for tool-sync in a few ways:

• Rewrote README
• Added a CHAGELOG
• Slightly changed the CONTRIBUTING.md guide (now it requires to add new changes in the changelog)
• Generated a new GIF with the new output
• Increased the version to 0.2.0

@MitchellBerend @FrancisMurillo @zixuanzhang-x please, double check the CHAGELOG.md file to make sure I haven't introduced any mistakes 🙂

I want to implement #54 and #55 before actually creating a release so the CHANGELOG will change. But those changes shouldn't affect the documentation so this one can be merged separately.

Additional tasks

• [x] Documentation for changes provided/changed
• [ ] Tests added

[chshersh]

Integration testing proved to be very useful!