feat(gatus): make replica count configurable in deployment values

[NerdySoftPaw]

This pull request makes the number of deployment replicas configurable in the Gatus Helm chart by introducing a new replicas field in values.yaml and updating the deployment template to use this value. This allows users to easily scale the deployment via Helm values.

Helm chart configurability:

• Added a new replicas field under deployment in charts/gatus/values.yaml to specify the desired number of replicas.
• Updated charts/gatus/templates/deployment.yaml to use the configurable deployment.replicas value instead of hardcoding the replica count.

Checklist

• Tested and/or added tests to validate that the changes work as intended, if applicable.
• Updated documentation in README.md, if applicable.

[TwiN]

Just to clarify, Gatus doesn't have a master/slave system that detects which one should send the request. They're really just separate Gatus instances, both sending their own requests and alerts. It would also mean that if an endpoint is down, there'd likely be two alerts sent

[NerdySoftPaw]

@TwiN thats what i hoped, maybe there are some people who wanna have more replicas of it because of using some configuration where each replica will be placed in a different zone or something else.
In most of the Helm charts a variable replica number is standard.
also there is a value of 1 as default so nothing will break. but if it makes no sense for you, feel free to close the MR, no prob with it :)