This adds:

- SQUARED LATIN CAPITAL LETTERs,
- NEGATIVE CIRCLED LATIN CAPITAL LETTERs,
- NEGATIVE SQUARED LATIN CAPITAL LETTERs,
- TORTOISE SHELL BRACKETED LATIN CAPITAL LETTERs and
- CIRCLED ITALIC LATIN CAPITAL LETTERs

Allows running the following command to execute the CLI

     $ python -m unidecode ...

https://docs.python.org/3/library/__main__.html

> For a package, the same effect can be achieved by including a
> __main__.py module, the contents of which will be executed when the
> module is run with -m.

Simpler and more forward compatible. The b prefix syntax is available on
all supported Pythons.

The Python project considers the optparse module as deprecated. See:

https://docs.python.org/3/library/optparse.html

> Deprecated since version 3.2: The optparse module is deprecated and
> will not be developed further; development will continue with the
> argparse module.

Replace the project's use with the newer argparse. The CLI is fully
equivalent and should not result in any backwards comparability
concerns.

https://docs.python.org/3/library/argparse.html

These codepoints are defined as "Greek small letter mu" and a Latin capital
letter, not with spelled-out unit names.

"u" is a common way of representing "micro" SI prefix in ASCII.