Add FREmu (non-linear matter power spectrum emulator for f(R) gravity)

[AstroBai]

Add FREmu to PyCCL.
One can set f(R)(Hu-Sawicki) parameter by setting
extra_parameters={"fR0":fR0}
Usage:
Install FREmu: pip install fremu
Set parameters:
fremu_nl = ccl.FREmu()
cosmo = pyccl.Cosmology(extra_parameters={"fR0":fR0}, matter_power_spectrum=fremu_nl)
Emulator details: https://arxiv.org/abs/2405.05840
Documentation: https://astrobai.github.io/codes/fremu.html
Source code: https://github.com/AstroBai/FREmu

[coveralls]

Pull Request Test Coverage Report for Build 9254894413

Details

• 11 of 34 (32.35%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.3%) to 97.131%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pyccl/emulators/fremu_pk.py	10	33	30.3%

Totals
Change from base Build 9021835287:	-0.3%
Covered Lines:	6567
Relevant Lines:	6761

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💛 - Coveralls