add support for custom deployment annotations

[victorpugin]

Description

Hello, we are willing to use elastalert2 at my company with https://github.com/stakater/Reloader to manage our rules in a custom configmap, but the chart doesn't allow to add deployment annotations. I propose to add that option.

Checklist

• [x] I have reviewed the contributing guidelines.
• [ ] I have included unit tests for my changes or additions.
• [ ] I have successfully run make test-docker with my changes.
• [x] I have manually tested all relevant modes of the change in this PR.
• [x] I have updated the documentation.
• [x] I have updated the changelog.

Questions or Comments

[jertel]

Hello, thanks for the contribution. Please confirm that the chart deploys with, and without custom deployment annotations, without any errors, and then check the "I have manually tested all relevant modes of the change in this PR".

[victorpugin]

Hello, thanks for the contribution. Please confirm that the chart deploys with, and without custom deployment annotations, without any errors, and then check the "I have manually tested all relevant modes of the change in this PR".

Hello @jertel, I manually tested the chart with and without the custom deployment annotation successfully in production, it's working well.