Add links to issues in the 3.0.0RC4, 3.0.0RC3, 3.0.0RC2, 3.0.0RC1 and 3.0.0a1 sections of the changelog

[rodrigoprimo]

Description

This PR adds links to all issues in the 3.0.0RC4, 3.0.0RC3, 3.0.0RC2, 3.0.0RC1, and 3.0.0a1 sections of the changelog. It also fixes a few typos.

Related issues/external references

Part of #244

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
  • This change is only breaking for integrators, not for external standards or end-users.
• Documentation improvement

PR checklist

• I have checked there is no other PR open for the same change.
• I have read the Contribution Guidelines.
• I grant the project the right to include and distribute the code under the BSD-3-Clause license (and I have the right to grant these rights).
• I have added tests to cover my changes.
• I have verified that the code complies with the projects coding standards.
• [Required for new sniffs] I have added XML documentation for the sniff.

[jrfnl]

I think it would be a good idea to keep these link lists in numeric order to prevent duplicate link definitions being added. Not much of an issue with short lists like the above, but it could be an issue for longer lists.
(here and elsewhere in this PR - I haven't noticed them not being in numeric order in previous PRs)

[rodrigoprimo]

Up to this point, I generated the list of issues in the order in which they appear in the changelog section for a particular version. I just pushed a new commit ordering the list of issues.

I will check the other lists added in previous PRs to see if any are out of numeric order, and if necessary, I will open a new PR to fix them.

[jrfnl]

Thanks! I'll be adding a markdown linter in CI at some point, which should also help prevent duplicate links from being added.

[jrfnl]

Thanks @rodrigoprimo ! LGTM and thank you for continuing your work on fixing up the changelog!