RFR: Cleaned up internal links and added a note-style [v2]

[Jesper Wilhelmsson]

> Pandoc doesn't require internal links to have the second "link"-part of the markdown link, so removing that throughout the guide to make it slightly easier to read the source.
> 
> Added a new note-style to clean up the source slightly more, and enable a consistent style for notes.
> 
> Added comment about not closing JBS issues with open sub-tasks.

Jesper Wilhelmsson has updated the pull request incrementally with one additional commit since the last revision:

  Note about using sub-tasks for problemlisting

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Changes:
  - all: https://git.openjdk.org/guide/pull/110/files
  - new: https://git.openjdk.org/guide/pull/110/files/fbabc225..fbec8aec

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=guide&pr=110&range=01
 - incr: https://webrevs.openjdk.org/?repo=guide&pr=110&range=00-01

  Stats: 2 lines in 1 file changed: 2 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/guide/pull/110.diff
  Fetch: git fetch https://git.openjdk.org/guide.git pull/110/head:pull/110

PR: https://git.openjdk.org/guide/pull/110