Improving formatting of valid chemical formulae

[ml-evs]

For now, this PR simply starts listing some rules on chemical formulae formatting that we can follow eventually, e.g.:

    chemFormulaFormat() {
      // Need to capture several groups, if the overall format doesn't apply, then
      // there should be no additional formatting whatsoever
      //
      // Some rules:
      //
      // * numbers between element symbols need to be subscripted, including "." and variables like "x"
      //    - e.g., Na3P => Na<sub>3</sub>P, Na3+xP => Na<sub>3+x</sub>P
      // * charges need to be handled separately and superscripted
      //    - e.g., Na+Cl- => Na<sup>+</sup>Cl<sup>-</sup>
      // * empirical labels for formula units like [pyr] must be left alone
      // * dots, when not used within numbers, must be treated as an interpunct "dot product" style dot
      //     - e.g., Cu2SO4.H2O => Cu<sub>2</sub>SO<sub>4</sub> · H<sub>2</sub>O

I think many of these can be handled selectively with some judicious regexes, and beyond formatting, the same rules could be used to validate e.g., empirical formulae in JS used for computing yields and the like.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.44%. Comparing base (4d53d7f) to head (b253762).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

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##             main    #1121   +/-   ##
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  Coverage   80.44%   80.44%           
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  Files          70       70           
  Lines        4771     4771           
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  Hits         3838     3838           
  Misses        933      933           

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[cypress]

datalab    Run #4008

Run Properties:   Passed #4008  •  95398d546f ℹ️: Merge b253762023fd368673d9e17d376e5d9fe523b53f into 4d53d7f10c6dae206bd59bd51c2c...

Project	datalab
Branch Review	ml-evs/chemform
Run status	Passed #4008
Run duration	06m 28s
Commit	95398d546f ℹ️: Merge b253762023fd368673d9e17d376e5d9fe523b53f into 4d53d7f10c6dae206bd59bd51c2c...
Committer	Matthew Evans
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---

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Failures	0
Flaky	0
Pending	0
Skipped	0
Passing	189
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[BenjaminCharmes]

@ml-evs I've pushed my changes for #1337 in this PR. If you'd prefer to do it in two separate PRs, I can create a new one.