updating-hub.md

Adding icons

• resource icon: save in /icons/${group}/${plural-name}.{svg,png}

• menu section icon: save in /icons/menu/${section-name}.{svg,png}

• Use lower case, remove any space in section name

Updating icons

Function List

• https://github.com/Masterminds/sprig/blob/master/docs/index.md
• https://github.com/kmodules/resource-metadata/blob/master/pkg/tableconvertor/templates.go#L48-L69
• https://github.com/kmodules/resource-metrics/blob/bf6b257f8922a5572ccd20bf1cbab6bbedf4fcb4/template.go#L26-L36