feat: pipx install

[qk-santi]

Allow users to easily install the cli tool using pipx
That will avoid having to install a venv, activate it, clone repo, install requirements...

pipx install git+https://github.com/monad-developers/staking-sdk-cli.git

Users will be able to upgrade versions simply doing

pipx upgrade --force staking-sdk-py

pipx won't be able to discover the version when calling for an upgrade, so we need to --force, but will show whatever is on src/staking_sdk_py/__about__.py after installing

Also, it'll allow to run the tool without installing

pipx run --spec git+https://github.com/monad-developers/staking-sdk-cli.git monad-staking-cli

Ideally a GH release action should be available so versioning can be do over tags, instead of the version file
That will allow to drop the --force option