Macro extension is done in two phases, attaching arguments and expanding
macros. Only in the first phase has a call to `parseArgspec`, so it
seems natural to deal with default arguments in the first phase. We
additionally attach default arguments to the AST during attachMacroArgs
and then it will be picked up by existing macro expanders. This breaks
an invariant that printRaw(attachArgs(X)) = printRaw(X).

Doing so required a rewrite of pegjs grammar use for parsing xparse
argument specifications. Previously, a lot of things were modeled by an
ArgSpec struct `Group`, but in the end those used in O,R,D and those for
e,E,u required different behavior in many aspects, so the pegjs grammar
now differentiate them via `group` and `collection`. Also, the ArgSpec
does not have Group anymore, everything is parsed to an array of
strings.

This should fix siefkenj#46.

Windows

Previously, the test was failing when run on Windows terminals due to
how it treats quotes passed as arguments. We now use 'cross-spawn'
module to get around of this issue.

Initially we have assumed that 'until's token list can be parsed in a
way similar to that of embellishments, but it turned out that there are
some differences. Thus, I have simplified pegjs grammar for until and
also worked out to make multi-token stop work.

Previously, typescript project references were used to wire imports
between workspace packages. Now this is done by package.json export
conditions. This nodejs feature has already been used to support
consuming packages in both esm and cjs format. We add an artificial
condition "_bundle", and use the respective bundler's export conditions
feature https://esbuild.github.io/api/#conditions and https://www.typescriptlang.org/tsconfig#customConditions
to achieve that IDE and TS compiler resolve any workspace package
imports to their respective Typescript source file, not their build
output .d.ts files.

This has an additional benefit of reducing bundle size of cjs build.
Previously, CJS build operated on ESM build output; They fed
dist/index.js files to esbuild. This changes this so that esbuild
directly operates on Typescript source files even in CJS build. As
esbuild will have more information, it will be able to better tree-shake
unused codes.

also used double quotes for interoparabilities with Windows

Until argspec's behavior was fixed, and while doing so, a support for
multi-token stops was added. Also, now it properly supports macro
delimiters (which was really just a by-product of applying uniform
treatment to any logic related to finding braces). This fixes
siefkenj#46.

In order to deal with default arguments referencing other arguments, it
seems to be better to move the logic from attachArgs to expandMacros.

Now expandMacros can correctly expand macros whose default arguments
reference other arguments. A special care was taken in order to follow
the behavior of xparse in case of circular references. In most of the
cases, xparse throws a compilation error, but it works in case like
`O{siefkenj#2} O{siefkenj#1}`. From this, we can reasonably guess that xparse treats
default arguments that directly copies another argument's value in a
special way. This behavior was implemented with a simple algorithm, and
it turns out to be consistent with xparse's behavior in cases considered
in unit tests.

Since package.json is re-written before publishing, we are free to point
`import` condition to `.ts` source files. However, CLI tests need to be
able to resolve to `dist/*.js` files, so a custom condition `prebuilt`
pointing to those are kept in every package.json.

The code path for optional argument without a default value wasn't being
tested. Added a test and fixed it so that it properly expands to
-NoValue-.