Explicitly use posixpath.join to join urls

[GrandMoff100]

Closes #101

[GrandMoff100]

MegaLinter status: ✅ SUCCESS

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ ACTION	actionlint	4		0	0.04s
✅ CREDENTIALS	secretlint	yes		no	0.87s
✅ GIT	git_diff	yes		no	0.02s
✅ JSON	eslint-plugin-jsonc	2	0	0	0.98s
✅ JSON	jsonlint	2		0	0.52s
✅ JSON	prettier	2	0	0	0.58s
✅ JSON	v8r	2		0	1.88s
✅ MARKDOWN	markdownlint	6	0	0	0.35s
✅ MARKDOWN	markdown-link-check	6		0	3.86s
✅ MARKDOWN	markdown-table-formatter	6	0	0	0.27s
✅ SPELL	misspell	26	0	0	0.06s
✅ YAML	prettier	7	0	0	0.71s
✅ YAML	v8r	7		0	6.76s
✅ YAML	yamllint	7		0	0.18s

See errors details in artifact MegaLinter reports on CI Job page