Add find_missing_groups function

[pw0908]

Things left to do in this branch:

• Add functionality to reduce the proposed set of groups to a minimal representation.
• Add tests
• Add docs
• Maybe clean-up the way environmental smarts are handled? (For groups where we've combined multiple heavy atoms, only specify environments for the atom which is bonding to another group)

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 95.53073% with 8 lines in your changes are missing coverage. Please review.

Project coverage is 83.20%. Comparing base (91ed072) to head (6742ff7).

Files	Patch %	Lines
src/missing_groups.jl	95.77%	6 Missing ⚠️
src/group_search.jl	94.59%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main       #5       +/-   ##
===========================================
+ Coverage   60.00%   83.20%   +23.20%     
===========================================
  Files           5        6        +1     
  Lines         245      399      +154     
===========================================
+ Hits          147      332      +185     
+ Misses         98       67       -31     

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[longemen3000]

support for .|| was added in 1.7 haha