Update changelog detailing Classes of Changes

[csarven]

Happy solstice!

This PR is a https://www.w3.org/2023/Process-20230612/#class-2 change in the specification updating the #changelog section in the following ways:

• Detailed use of language and links from W3C Process Document's Classes of Changes in the changelog.
• Uses a table with columns Change Class, Subject, and Description to further detail editorial, substantive, registry changes in the specification since the previous version. Each row in the table corresponds to a specific "change".
• Adds link to list of issued addressed.
• Adds link to W3C diff service between this version and previous version.
• Adds link to GitHub for detailed log of changes.
• Adds link to changelog of previous version to discover earlier versions.
• All change information is machine-readable (RDF) and expressed using Spec Terms.

This approach to the changelog was demo'd in Test Suite Panel 2023-04-18 meeting: https://github.com/solid/test-suite-panel/blob/main/meetings/2023-04-18.md - the minutes do not capture the details of the live demo) as part of the Solid QA work and deemed to be useful in specifications.

To help the PR reviewers, detailed information on "Classes of Changes" were originally introduced in some Solid PRs, e.g.:

• https://github.com/solid/specification/pull/524
• https://github.com/solid/specification/pull/479
• https://github.com/solid/specification/pull/478
• https://github.com/solid/notifications/pull/174
• https://github.com/solid/notifications/pull/169

A link to the diff view was also used in numerous PRs, e.g., https://github.com/solid/specification/pull/491 (as well as inspired by W3C Process's own Changes)

Hence, the approach here is the initial codification of the practise across W3C Process, Spec Terms, PR information for use in the specification. PRs introducing editorial, substantive, and registry changes can continue to mention the correction class in the PR description.

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Merging this PR as it updates the non-normative section, and with some preference to get this initial approach going as is. Still, feedback and improvements are most welcome!

[csarven]

Use: . Live / accessible from https://solid.github.io/notifications/protocol . Information in spec:Changelog is used in the diff view of dokieli where the requirements meet.

While implementing its consumption, I've noticed that the changelog section (table) did not originally include some of the changes that were made to the requirement. So, the tool helped me, as an editor/author to include that change information.