Document using xcstrings-tool cli directly

[liamnichols]

• Part of Better support for use in open source libraries #32

this change adds documentation for using the cli directly in advanced use cases (or when SPM plugins are bugged)

[github-actions]

✅ Pull Request passed benchmark checks

Summary

Sat Jun 29 08:22:38 UTC 2024

===========================================================================================================
Threshold deviations for StringGenerator.generateSource(for:tableName:accessLevel:):XCStringsToolBenchmarks
===========================================================================================================

Time (total CPU) (ms, %)	main	pull_request	Difference %	Threshold %
p25	982	1047	6	5
p50	982	1047	6	5

New baseline 'pull_request' is WORSE than the 'main' baseline thresholds.

---

Comparing results between 'main' and 'pull_request'

Host 'Mac-1719647334730.local' with 3 'arm64' processors with 7 GB memory, running:
Darwin Kernel Version 23.5.0: Wed May  1 20:12:39 PDT 2024; root:xnu-10063.121.3~5/RELEASE_ARM64_VMAPPLE

XCStringsToolBenchmarks

StringGenerator.generateSource(for:tableName:accessLevel:) metrics

Time (total CPU) (ms) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	982	982	982	1026	1026	1026	1026	2
pull_request	1047	1047	1047	1047	1047	1047	1047	1
Δ	65	65	65	21	21	21	21	-1
Improvement %	-7	-7	-7	-2	-2	-2	-2	-1