Add support for specifying ignore rules in .clang-format-ignore file using gitignore syntax

[lopopolo]

Closes #55.

This is a fairly large rewrite of this small package.

The flow of the CLI program is reworked to the following stages:

• Walk given directory, recursing into all directories, and yielding paths to files that end in the given extensions.
• Relativize the yielded paths to the given directory, filter with ignore, and absolutize the paths.
• Format or check sources.
• Print report.

These refactors contain many performance optimizations which make file path walking and path filtering much faster.

To support this new flow, this PR adds two new options to the CLI, in the style of eslint:

• --ext, which specifies the comma-separated set of file extensions to include for formatting. Default: .c,.cc,.cpp,.h
• --ignore-path, which specifies the path to a clang-format ignore file. Default: .clang-format-ignore.

The .clang-format-ignore file is parsed with the ignore npm package, which is compatible with the gitignore spec.

This PR also adds the ESM-only chalk v5 dependency for slightly nicer colorized reporting. I upgraded the package to ESM (mostly by converting require to import and changing export syntax; I also had to replace __dirname).

clang-format --help

$ npx . --help
Usage: clang-format [options] [directory]

Node.js runner for LLVM clang-format

clang-format is a tool to format C code.

If no arguments are given, the runner formats the current directory recursively.
Any clang-format configuration present on the filesystem will be honored.

--check mode is suitable for CI. --check does not attempt to format and instead
exits with a non-zero status code if the source code on disk does not match the
enforced style.

Options:
  -V, --version         output the version number
  -c, --check           check if the given files are formatted. Exit with a non-
                        zero status code if any formatting errors are found.
  --ext <extensions>    specify formattable file extensions (default: ".c,.cc,.cpp,.h")
  --ignore-path <path>  specify path of ignore file (default: ".clang-format-ignore")
  --no-ignore           disable use of ignore files and patterns
  -h, --help            display help for command