Draft initial how-to-parse "base" and "advanced" examples #856

[johnmhoran]

Reference: #856

[johnmhoran]

@mjherzog As a guide to the 4 example .md drafts, these are the test candidate PURL strings (just excerpts) parsed in each file:

Filenames vs contents

• purl_2026-05-12_16-45-04.md -- alpm/arch/containers-common
• purl_2026-05-12_16-45-10.md -- npm/%40babel/core
• purl_2026-05-12_16-45-15.md -- apk/alpine//apk
• purl_2026-05-12_16-45-20.md -- golang/google.golang.org//extra_segment//genproto

[johnmhoran]

@mjherzog I've added the May 14 draft how-to-parse -- same structure as the May 12 draft, with a different candidate input PURL. I think we should use those as the source of the next iteration.