Release 1.3.19.0

[rpo-fr]

OpenSearch 1.3.19 has been released, see release notes.

Checklist:

• [x] Compatibility Matrix is updated (https://github.com/Aiven-Open/prometheus-exporter-plugin-for-opensearch/pull/309)
• [x] Release 1.3.19.0 tag is present in the repo
• [x] Release artifacts are available and downloadable
• [x] Release notes published
• [x] Forum announcement published

[javsalgar]

I'm also missing version 1.3.18, which was released on 2024-07-09

[lukas-vlcek]

@javsalgar Opening a ticket for Release 1.3.18.0: https://github.com/Aiven-Open/prometheus-exporter-plugin-for-opensearch/issues/304