docs: add CC BY 4.0 license

fix: add cross-links to ctf-workflow checklist

fix: add cross-link to google-dorking in osint file

fix: add table of contents to all long files

update: README opener

add: advanced, ctf-workflow, what-next content — all 22 files complete

add: smb-enumeration, other-services, wordlists content

add: what-is-enumeration, web-enumeration, dns-enumeration content

init: add .gitignore