✨ Allow deployment config to provide translation overrides

[JGreenlee]

✨ Allow deployment config to provide translation overrides

A generic way for deployments to tweak any i18nized text in the app, specified as "translation_overrides": {"": { ...same shape as en.json... }}

Via i18next addResourceBundle, these get tacked onto the translations from en.json, es.json, etc. when the config is loaded, which is before the UI gets a change to load any strings that would be modified.
The exception is, of course, the strings that appear before the user enters their opcode (as the app doesn't know what deployment it's using yet!)

We can likely use this to replace intro.translated_text entirely, since it accomplishes the same thing in a more generic way.

We might also consider using it to replace label-options "translations"; i.e. instead of asking deployers to provide the translations there for all the modes they list, we provide the translations for our default set of modes, and they would only have to provide the ones they added (or wanted to name something else), and those translations would live in the same place as any other translations/ in-app text they are providing.

[codecov]

Codecov Report

❌ Patch coverage is 95.65217% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 30.03%. Comparing base (2dcf3f6) to head (d1f3654).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
src/js/i18nextInit.ts	94.11%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1275      +/-   ##
==========================================
+ Coverage   29.64%   30.03%   +0.38%     
==========================================
  Files         134      134              
  Lines        4814     4835      +21     
  Branches     1218     1215       -3     
==========================================
+ Hits         1427     1452      +25     
+ Misses       3373     3370       -3     
+ Partials       14       13       -1     

Flag	Coverage Δ
unit	30.03% <95.65%> (+0.38%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/js/config/dynamicConfig.ts	80.50% <100.00%> (+0.68%)	⬆️
src/js/i18nextInit.ts	76.74% <94.11%> (+11.35%)	⬆️

... and 2 files with indirect coverage changes

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