[Docs] Update rules authoring documentation to explicitly call out required files in regard to a ruleset

[jwmatthews]

To help avoid confusion from new users creating custom rules, lets do a pass over the rules authoring content and be explicit on what fields are required or optional.

Specifically, ensure we go over the section on the ruleset file:
https://github.com/konveyor/analyzer-lsp/blob/main/docs/rules.md#ruleset

This issue is from some confusion we've seen in past where the name parameter was not set on a ruleset and it caused the custom rules to not work.

[konveyor-ci-bot]

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