docs: add new contribs

[mihai-sysbio]

Main improvements in this PR:

This PR adds new contributors, also achieving the aim of the closed PR #543.

I hereby confirm that I have:

• Tested my code on my own computer for running the model
• Selected develop as a target branch
• Any removed reactions and metabolites have been moved to the corresponding deprecated identifier lists

[mihai-sysbio]

@manas-kohli and @juliette-cooke thank you for your contributions! Sorry I forgot to ask you if you would like to provide your ORCiD to be included with your contribution. Even though this PR was merged, we'll open a new one and make the necessary corrections.
@haowang-bioinfo, perhaps we can wait with the 1.15 release a little longer until the contributions get amended.

[haowang-bioinfo]

@haowang-bioinfo, perhaps we can wait with the 1.15 release a little longer until the contributions get amended.

the release 1.15, which is really oversized, probably has no conflict with amending contribution, which can always be updated later on GitHub