Improve how references are used throughout Physlib

[Alex-Zughaid]

• References section at the top of the file
• Each reference must appear in the BibTex file
• The bib ID should appear next to the reference within the Lean files, however we still keep name/author etc. to ensure human readability
• Added check_references.py which uses regex to check these rules are followed (Similar to lint_bib.sh in mathlib)
• if you have no references but have a ##References section add * None to make prevent the regex from breaking.

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[Alex-Zughaid]

Very big PR - important files are references.bib and check_references.py

[jstoobysmith]

Could you make a comment on the relevant Zulip channel about this?