chore: Configure Chart signing

[lusu007]

Description

Fixes #9

Additional Context

N/A

Checklist

• [x] The chart version in Chart.yaml has been updated according to semantic versioning (semver). This update is not required if the changes only impact README.md files.
• [x] All variables are document in the Chart's values.yaml and README.md files.
• [x] The pull request title meets the Conventional Commits specification and includes the chart name, for example: feat(chart-name): Add replica support

[lusu007]

I believe a version bump is unnecessary. What are your thoughts, @meyfa?

[meyfa]

I believe a version bump is unnecessary. What are your thoughts, @meyfa?

I agree. We'll get a signed release on the next regular release.

[lusu007]

• [x] Add key to Chain of Trust (Keybase.io?)
• [x] Document how an end-user could verify our charts