Update latest zig version pretty was tested on

Add U21 print option (#12)

A `u21` is a weirdly specific thing to use as a number, I thought it
would be nice if it printed as a character by default. I think this 
is correct for pretty also. If we say "u21s are characters" then 
silently switching to decimal printing when they don't fit is a weird
thing to do.

* Add u21_is_codepoint option, default true
* Test over-sized u21. Turns out Zig doesn't panic (good) and uses 
  the replacement character.
* Update comment and README

Use std.debug.print in test mode (fixes #9), add `.zig-*` to .gitignore

This patch changes `pretty.print` to use `std.debug.print` when in test
mode, to avoid whatever race condition with the progress bar was making
the 0.12 version hang under those conditions.

Also adds `.zig-*` to .gitignore, to handle the new dotted name for the
cache directory.

Zig 0.13 compat (#8)

Update build.zig to 0.13 syntax (#8, fixes #7)

Replace the pre-0.13 syntax for paths with it's 0.13 equivalent.

Optimize printing type info conditions for inline mode

Fix small typos in options documentation

Fix #2 and merge #3. The changes introduced:

- Introduce four options to distinguish between `"strings"` in arrays and slices.
- Remove `typeIsArrayString` as it is no longer necessary.
- Update tests to reflect the change, including the ones from Zig itself.

Release v0.9.3

Fix the ability to interpret `[n:0]u8` as a string

Fix demo to reflect version changes