Add missing ref, fix list issue, fix nav bar, cleanup Markdown formatting

[bact]

Update 2024-07-11, this PR will be closed as some docs are moved to spdx/using repo.

• docs/annexes/diffs-from-previous-editions.md -- now in new PR Use H2 for headings in Annex A #988
• docs/annexes/getting-started.md -- now in spdx/using repo
  • Add missing ref of [Property_externalIdentifierType] -- already fixed by other PR
• docs/annexes/using-SPDX-to-comply-with-industry-guidance.md -- now in spdx/using repo
  • Remove extra space at the end of [Core/Classes/Artifact.suppliedBy ] -- will fix in spdx/using repo
• Cleanup Markdown formatting
  • Apart from keeping consistency, this is also to avoid any possible rendering issue due to Markdown-flavour incompatibility between GitHub and mkdocs.
  • Fix list issue in Serialization chapter -- now in new PR Fix bullet list in Serialization chapter #990
  • Fix list issue in Annex F - F.2 -- in new PR Fix Markdown lint warnings to avoid rendering issue using#2
  • See more details in a similar fix at SPDX v3 Model: Doc: Fix list and nested list rendering issues in spec webpages + other Markdown format cleanup spdx-3-model#723

[bact]

The list issue (list rendering incorrectly if there's no blank line before the list) is a known issue since 2.3.1, see #825

[goneall]

LGTM - Thanks @bact

[bact]

Will close this PR as some of the docs here are already transferred to spdx/using repo (spdx/using#1), will continue to fix there instead.

Some other fixes will be open as new PRs.