Add changelog to main readme

[ElectricRCAircraftGuy]

I volunteer.

I'll model it after this one: https://github.com/ElectricRCAircraftGuy/PDF2SearchablePDF#changelog.

Feel free to give me push access if you like since I'm opening up a lot of PRs and issues.

[nimrod46]

That will be great, once I have the right permissions here I will give you push access