refactor: avoid nullish coalescing operator (??)

[mlrawlings]

Description

Avoids the usage of the nullish coalescing operator (??)

Old

<div class=`${value ?? ""}`/>

New

static function _toString(value) {
  return value == null ? "" : value;
}

<div class=`${_toString(value)}`/>

Motivation and Context

As this is a compat layer for applications that existed before ?? was part of the language, there have been instances where existing application dependencies (older versions of babylon for instance) don't support the new syntax.

Screenshots (if appropriate):

Checklist:

• I have updated/added documentation affected by my changes.
• I have added tests to cover my changes.

[codecov]

Codecov Report

All modified lines are covered by tests ✅

Comparison is base (5f39ccd) 87.95% compared to head (757e1c4) 88.03%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #14      +/-   ##
==========================================
+ Coverage   87.95%   88.03%   +0.07%     
==========================================
  Files          55       55              
  Lines        4759     4790      +31     
  Branches      718      719       +1     
==========================================
+ Hits         4186     4217      +31     
  Misses        551      551              
  Partials       22       22              

Files	Coverage Δ
...rc/migrate/non-standard-template-literals/index.ts	86.58% <100.00%> (+3.12%)	⬆️

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