Token filters - keyword_repeat [DOC]

[AntonEliatra]

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Create a separate page for Token filter: keyword_repeat

Part of META issue: https://github.com/opensearch-project/documentation-website/issues/1483

*Version: all

[AntonEliatra]

Skipping this for now, as it needs to reference stemmer and porter_stem token filter, which are not yet completed

[Naarcha-AWS]

Making this as blocked for now until stemmer and porter_stem are merged.