src: Use UnicodeError instead of UnicodeDecodeError ...

MicroPython doesn't support UnicodeDecodeError, just UnicodeError.

main: Use new parser if NEWLANG_NEW_PARSE is set ...

This is not intended to be actually used outside testing compatibility
with micropython as we don't actually have tests on it yet.

tests: Minor whitespace fix

parse: Create messages from ParseTasks

parse: Add filename to error messages

parse: Create messages from ParseErrors

parse: Rename ParseError messages to ParserError

tests: Tidy parse error test data

parse: Don't generate message ids, use a table ...

I've decided that all translation strings should be used in source code
as-is without any kind of building.

parse: Add function to fully format an error

tests: Always draw a task for ParseContext

parse: Add function to format a ParseContext for display

parse: Add function to format a ParseErrorException for display

tests: Document parse error data structures

tests: Fix draw_maybe ratio ...

I wrote this code while really tired and of course an off by one error
slipped in.

tests: Use a proper values for structural ParseContext tests

src: Check for None in all __eq__ methods ...

This lets us finally compare parse error exceptions and contexts of
different shapes.

main: Put executable name in usage

main: Add run_file function for REPL use ...

This should help using NewLang from micropython.

log: Rely on main for the getenv call ...

micropython on the Pi Pico for some reason doesn't support getenv, so
try and push this in to main where we can decide to use it.

main: Remove unused nowait_main function

port: Add micropython-compatible atexit wrapper

run: Use run.py to run src/main.py ...

This completely removes the weird logic for editing paths at the expense
of some more code.

i18n: Add mutation tests

i18n: Add new module containing a Message class ...

This Message class will be used to format localized text later.

tests: Move parser error tests to its own file

parse: Have parse run parse_file

parse: Actually add parser code for real this time I promise

parse: Add file parser

parse: Add directive parser