[DOC] Character filters - Pattern replace

[leanneeliatra]

Description

Updating the OpenSearch documentation to include a page on Pattern Replace filters in the Character filter analyzers section.

Issues Resolved

Part of #1483 addressed in this PR.

Version

all

Frontend features

n/a

Checklist

• By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license and subject to the Developers Certificate of Origin.
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[github-actions]

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[vagimeli]

@udabhas @varun-lodaya Please provide tech review approval to move this PR forward in the documentation process. Please ensure content and code examples are relevant and accurate. Thank you.