Updates compiler, headers and documentation for the 'name' section,
which will always be present as the LDML keyboard spec requires at least
one name in the `<names>` element.

Also uses `index()` to get count of strings automatically.

Reformat basic.txt to make it more readable as it will get less
'basic' over time!

Adds an `index` command as suggested by #7186.

> Future enhancement suggestion: include ... index() for block indices
> within these repeated blocks. Would be very useful for string tables
> in the example ref.

Also adds semver package for validating the version field.

This makes it easier to write a binary file which contains offsets and
size values. Using this for unit tests for the LDML keyboard compiler.

Example kmldmlc basic.txt is updated and included.

Future enhancement suggestion: include count() for repeated blocks and
index() for block indices within these repeated blocks. Would be very
useful for string tables in the example ref.

This is reasonably random, but wanted to add another test for content
rather than structure, just to verify that the DTD-XSD-jsonschema
translation is doing the right thing according to what we expect.

Looking good.

As we do not appear to have access to a good DTD validation library in
Node.js, we will instead convert the DTD to a JSON schema file and use
that for validation.

I have not verified every aspect of the JSON schema at this point, but
will incrementally do so as I implement further aspects of the compiler.

This updates all the testing to use the schema. As the schema validation
is slow, I have increased the 'normal' time for tests.

Also removes `-test` from normal `make build` for kmlmc, moving that
responsibility to `make test` (but uses `-tdd` to avoid rebuild).

feat(developer): loca minimization + cleanup kmldmlc error list 🙀

feat(developer): add loca tests 🙀

chore(core): split out validators 🙀

feat(developer): add unit tests for meta compiler 🙀

- copy over asserts from 'old' code

#7136

yes, a kmxplus file does not start with a 'sect' !

#7136

#7136

chore: merge master into feature-ldml 🙀

Yeah two for the price of one:

- minimize locales at compile time
- cleans up the list of errors to make it easier to maintain and use

Note: bumps target to es2020 for better Intl.* support. Verified as
supported by Node 16+ and modern browsers.

Adds support for multiple locales and basic canonicalization. Does not
support normalization of locales.

chore(developer): Merge branch 'chore/merge-master-into-feature-ldml' into feat/developer/kmldmlc-meta-tests-and-cleanup

Merge pull request #7153 from keymanapp/refactor/developer/kmldmlc-pure-functional-section-compilers

refactor(developer): each section compiler is a pure function 🙀

feat(core): set -DDEBUG for debug 🙀

auto: increment master version to 16.0.55

- set -DDEBUG for 'debug' meson builds
- default KXPLUS_DEBUG  to 1 for -DDEBUG

#7136

First, a little bit of refactoring to make it cleaner to do unit test
for each section.

Then add some global error values.

Throw in a helper function or two.

Dust off the edges of the CompilerCallbacks object.

Duct tape together validation of the normalization attribute.

And ... eventually we get a nice clean-like unit test for the meta
compiler, with three pretty little fixtures and as-neat-as-you-like-it
assertions.

chore(core): emcc off path for linux

Merge pull request #7151 from keymanapp/refactor/developer/kmldmlc-compiler-separate-files-for-sections

refactor(developer): separate files for kmldmlc sections 🙀

chore: merge master into feature-ldml 🙀

Well, almost. There are still callback side-effects for messages. These
may in future be returned as an array as well, eliminating the need for
a message callback.

But restructures each section compiler so that it is self-contained and
responsible only for writing its own section. Also tightens up the types
for the sections constants.

Last, but not least, moves responsibility for writing the output .kmx
out of compiler.ts and into its callers -- removing one dependency from
the compiler. Reading input files still needs to be done in the
compiler, as there may be multiple input files with `<import>` that we
cannot know about until we start parsing xml.

fix(linux): Allow downgrades for installing build deps

fix(core): ldml: fix validator 🙀

chore(linux): Update debian changelog 🍒