Integrate minimum individual heat pump capacity

[ClaraBuettner]

egon-data calculates the minimum capacity of individual heat pumps to make sure, that all houses which have a heat pump have enough capacity.
The value is written into a csv file (https://github.com/openego/eGon-data/blob/da196626a988f69a7a6020884a844d3248201a9a/src/egon/data/datasets/heat_supply/individual_heating.py#L1624-L1647).
This data needs to be used in pypsa-eur-sec, I guess in prepare_sector_network.py.
Heat pumps are added here:

pypsa-eur-sec/scripts/prepare_sector_network.py

Lines 1494 to 1504 in 6b099a7

	n.madd("Link",
	nodes[name],
	suffix=f" {name} {heat_pump_type} heat pump",
	bus0=nodes[name],
	bus1=nodes[name] + f" {name} heat",
	carrier=f"{name} {heat_pump_type} heat pump",
	efficiency=efficiency,
	capital_cost=costs.at[costs_name, 'efficiency'] * costs.at[costs_name, 'fixed'],
	p_nom_extendable=True,
	lifetime=costs.at[costs_name, 'lifetime']
	)