[DOC] Improve anomaly detector documentation

[CodeLionX]

Reference Issues/PRs

none

What does this implement/fix? Explain your changes.

• removes some checks from the numpydoc validation
• add discussion of detector learning types to BaseAnomalyDetector
• fixes some documentation warnings
• adds capability tables to existing detector documentations

Does your contribution introduce a new dependency? If yes, which one?

no

PR checklist

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• [x] The PR title starts with either [ENH], [MNT], [DOC], [BUG], [REF], [DEP] or [GOV] indicating whether the PR topic is related to enhancement, maintenance, documentation, bugs, refactoring, deprecation or governance.

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I have added the following labels to this PR based on the title: [ $\color{#F3B9F8}{\textsf{documentation}}$ ]. I have added the following labels to this PR based on the changes made: [ $\color{#6F6E8D}{\textsf{anomaly detection}}$ ]. Feel free to change these if they do not properly represent the PR.

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