Adding icon so chart passes helm lint

[adamhaney]

Helm lint recommends that charts include an icon. I added one that was already hosted on the website

Helm Lint Output Before Change

➜  botkube git:(master) ✗ helm lint .
==> Linting .
[INFO] Chart.yaml: icon is recommended

1 chart(s) linted, no failures

Helm Lint Output After Change

➜  botkube git:(master) ✗ cat Chart.yaml 
apiVersion: v1
appVersion: "1.0"
description: A Helm chart for Kubernetes
icon: https://www.botkube.io/images/botkube.ico
name: botkube
version: 0.1.0


➜  botkube git:(master) ✗ helm lint .
==> Linting .
Lint OK

1 chart(s) linted, no failures

[bhavin192]

Hey @adamhaney, thank you for your contribution 😄