Include export store options

[energyLS]

Closes #156

Despite tackling #156 (which has been tested successfully), this PR includes the option to add costs to the "dummy" export store.

Changes proposed in this Pull Request

This PR includes more options to configure the export store. System effects of different settings are currently investigated.

Checklist

• [x] I tested my contribution locally and it seems to work fine.
• [x] Code and workflow changes are sufficiently documented.
• [x] Newly introduced dependencies are added to envs/environment.yaml and envs/environment.docs.yaml.
• [x] Changes in configuration options are added in all of config.default.yaml, config.tutorial.yaml, and test/config.test1.yaml.
• [x] Changes in configuration options are also documented in doc/configtables/*.csv and line references are adjusted in doc/configuration.rst and doc/tutorial.rst.
• [x] A note for the release notes doc/release_notes.rst is amended in the format of previous release notes, including reference to the requested PR.

[energyLS]

These are some results for Morocco. Applying costs to the export store increases the objective hence total system cost and prevents the overdimensioning of the export store. If no store is allowed, the system store H2_GWh increases accordingly. The results seem reasonable.

[energyLS]

@hazemakhalek could you add your review? :)

[energyLS]

pre-commi.ci fails due to "(timeout after 180 seconds)" but not sure why:

If I try pre-commit run --all-files on my local machine it works fine:

@davide-f do you maybe know why?