feat: add flipt k8s stack (MAR-4514)

[markphelps]

BACKGROUND

• Add information about the background and reason for the change.

Adds flipt stack to K8s marketplace re: MAR-4514

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Changes

• List the changes that you made

Addition of Flipt stack

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Checklist

• review the contributing doc with steps for both adding or updating your application (if applicable)

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Reviewer: @marketplace-eng

[github-actions]

👋 @markphelps
If this is an EXISTING Marketplace app, now that the PR is merged, all new users of your app will get the current version. You should visit the Vendor Portal to make sure you update any version numbers, Description, or Getting Started information that are related to the merged PR.
If this is a BRAND NEW Marketplace app, before this app update can go live on the Marketplace, please update and submit your app from the Vendor Portal.
Thanks!