Script to build language data JSON automatically

The script hardcodes the names of its input files and expects them to be
in the same directory as the script. (Or rather, the current working
directory, which if the script is executed as "python scriptname.py"
will be the script's directory). The filenames are listed near the top
fo the script, so if its inputs ever change it will be easy enough to
edit the filenames.
Tweak language script: don't mark dialects

Instead of putting " (dialect)" or " (pejorative)" after alternate
language names that represent dialects or pejorative names (like Auca
for the Waorani, for instance), we'll just output a list of bare names.
The intended users of this data are expected to know the language
they're working in well enough to know which names are pejorative, which
represent dialects, and so on.
Language JSON script: ensure field presence, order

Rename fields to be consistent with the Javascript code that's going to
parse them, and also ensure that the fields will always be output in the
same order: name, code, country, altNames. Also, any languages with no
alternate names will be guaranteed to have an altName property (which
will be an empty list). However, languages without a two-letter code
will *not* have a code.two property; it will be undefined. All languages
are guaranteed to have a code.three property, though.
Language JSON script: produce Javascript, not JSON

Automatically produce a file suitable for drop-in replacement in the
Javascript code managing input systems in LanguageForge.
Language JSON script: write script and region data

Note that the script data is different from the prototype: the prototype
only had one name per script ("Latn" -> "Latin"), but the actual IANA
subtag registry data has some scripts with multiple names. Some are
spelling variants like Hangul, Hangŭl, and Hangeul, but others are very
different names like Ethiopic and Ge'ez. (Same script, with subtag Ethi).
So the Javascript code that relies on inputSystems_scripts.js will need
to be modified a bit, to take a list of names rather than a single name.
Auto-generated language, region, script data

The Python script to create these three files can be found in the
"src/scripts/language picker" directory.