Fixes#193
Add the ability to specify a custom SponsorBlock API server. (draft implementation by copilot-workspace)
* Add a new configuration option `api_server` in `config.json.template` to specify the custom API server URL.
* Remove the hardcoded `SponsorBlock_api` URL from `src/iSponsorBlockTV/constants.py`.
* Update the `ApiHelper` class in `src/iSponsorBlockTV/api_helpers.py` to use the `api_server` configuration option for API calls.
* Add an option to input a custom API server URL in the CLI setup in `src/iSponsorBlockTV/config_setup.py`.
* Add an option to input a custom API server URL in the graphical setup wizard in `src/iSponsorBlockTV/setup_wizard.py`.
* Set the default `api_server` to "https://sponsor.ajay.app" in `src/iSponsorBlockTV/helpers.py`.
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For more details, open the [Copilot Workspace session](https://copilot-workspace.githubnext.com/dmunozv04/iSponsorBlockTV/issues/193?shareId=XXXX-XXXX-XXXX-XXXX).
