RFR: Section on sponsoring [v11]

[Jesper Wilhelmsson]

> Copied and updated the text from the old sponsoring page: https://openjdk.org/sponsor/
> The purpose is to have the sponsor link on the OpenJDK page lead here instead.
> 
> Also updated the contributing section with some parts taken from the old contributing page: https://openjdk.org/contribute/
> Again, the intention is to change the link on the OpenJDK page to lead here.

Jesper Wilhelmsson has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 29 commits:

 - Merge branch 'master' into contribute
 - More fixes after review
 - Fixes after review
 - Be mindful
 - Unmess
 - Merge branch 'contribute' of github.com:JesperIRL/guide into contribute
 - Merge branch 'master' into contribute
 - Merge branch 'contribute' of github.com:JesperIRL/guide into contribute
 - Added words
 - Fixed review comments
 - ... and 19 more: https://git.openjdk.org/guide/compare/84d736ee...821e54c9

-------------

Changes: https://git.openjdk.org/guide/pull/97/files
 Webrev: https://webrevs.openjdk.org/?repo=guide&pr=97&range=10
  Stats: 91 lines in 5 files changed: 84 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/guide/pull/97.diff
  Fetch: git fetch https://git.openjdk.org/guide.git pull/97/head:pull/97

PR: https://git.openjdk.org/guide/pull/97