Tidy requirements for plugin metadata

Currently, the requirements for plugin IDs lack some information, and are scattered:

• The requirement for plugin ID is described in:
  Manifest - Developer Documentation

  And the requirements for the plugin description is documented in:
  Submission requirements for plugins - Developer Documentation

• A plugin ID "must only contain lowercase ASCII letters and hyphens" according to the "risk" message in the new Obsidian Community site's scorecards, e.g. Orgmode (CM6) - Obsidian Plugin. That is not documented.

Additionally, it is impossible to change a plugin ID after the first submission without the help of Obsidian team.

The following modification would be great.

• Gather requirements into the "Submission requirements for plugins" page.
• Document plugin ID requirements about allowed characters in the "Submission requirements for plugins" page.

Start with the Submission requirements for plugins page and compare it with the linked Manifest - Developer Documentation page and the example Community scorecard. Consolidate the plugin ID and description requirements there, add the documented character restriction for plugin IDs, and confirm that the resulting page contains all requirements requested by the issue.