Update license (#2)

This pull request involves the removal of several files and updates to
the `README.md` file. The most important changes include the deletion of
the funding configuration, the code of conduct, and the license file, as
well as formatting improvements in the `README.md`.

Deletions:

*
[`.github/FUNDING.yml`](diffhunk://#diff-07985fdcade0e64d11482724879a644f07879ba61b8fb6c6119e1b1902b72ae4L1-L12):
Removed the funding configuration file.
*
[`CODE_OF_CONDUCT.md`](diffhunk://#diff-ffdbe3a1e7ee93cacfc080b6c635ccf3a8f6b0f00f2fb884f78c6b5f9dac8fd2L1-L128):
Removed the code of conduct document.
*
[`LICENSE`](diffhunk://#diff-c693279643b8cd5d248172d9c22cb7cf4ed163a3c98c8a3f69c2717edd3eacb7L1-L21):
Removed the license file.

These were removed in favor of the `COPYING` file for GNU's GPL license,
and now both the code of conduct and funding comes from the user-wide
configuration. Inheriting [this code of
conduct](https://github.com/alDuncanson/.github/blob/main/CODE_OF_CONDUCT.md)
and [this funding
file](https://github.com/alDuncanson/.github/blob/main/FUNDING.yml).

Updates to `README.md`:

* Improved badge layout and added a new badge for the Contributor
Covenant.
* Reformatted instructions for downloading and importing the color
scheme file for better readability.
* Reformatted the Zsh theme link for better readability.

replace coffee button