parse: Pass a context to the parse function

mutmut: Run pytest with -n auto ...

This doubles the speed of testing.

env.sh: Unset internal commands

parse: Have parse_text handle contexts properly

parse: dNonnescent -> descent ?

parse: Have parse_bool handle contexts properly

main: Fix spacing

main: Add a main function that waits ...

This is enabled in the zipapp to make life easier when the program is
run from a GUI.

make: Drop in favor of build.py

build: Add script to build NewLang.pyz

env.ps1: Us python -m pip to avoid weird bugs ...

The Python.Python.3 package on Windows seems to break if you try to
update pip using the pip command. Maybe because the pip binary is in use
during the upgrade?

env.sh: Use python3 for wider compatibility

env: Fix venv path

make: Drop what env does

env: Add domut for mutmut testing

.gitignore: Hide venv directory

env.sh: Add Unix env.sh

env.ps1: Prefix commands with 'do' to avoid namespacing

env.ps1: Add Windows environment for development

tests: Clarify test name in test_clear_notes

parse: Use an error context for clear_notes

src: Pass a parent context to skip_note

parse: Have skip_note create a PARSE_NOT ParseContext

parse: Use __repr__ instead of __str__

parse: Pass a ParseContext to read_token

parse: Allow attaching a ParseContext to a ParseErrorException

parse: Add parse contexts for later error reporting

tests: Fix ParseError exception tests not wroking

tests: parse: Remove unused insert_random

tests: parse: Clean up some includes