Update glossary.md

[NicolasLiampotis]

Add initial glossary

[github-actions]

Mega-Linter status: ⚠️ WARNING

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ CREDENTIALS	secretlint	yes		no	0.79s
✅ GIT	git_diff	yes		no	0.02s
⚠️ MARKDOWN	markdownlint	1	1	2	0.32s
✅ MARKDOWN	markdown-link-check	1		0	0.39s

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