Add FEATURE_SETTING_STOCK_COUNT_OPENED_PRODUCTS_AGAINST_MINIMUM_STOCK_AMOUNT to configurable features

[Kackerlacka]

Problem/Motivation

I would like to be able to have it so opening a product in Grocy does not count against the minimum stock amount. This setting is available in config-dist.php, but not one of the configurable options for the HA addon.

Expected behavior

Should be able to configure this option.

Actual behavior

Unable to configure the option.

Steps to reproduce

Nothing to reproduce.

Proposed changes

Add the configurable option to the configuration section in the Grocy addon.

[tringler]

@Kackerlacka I created a PR for that #151