Add CSS class map pattern entry to conventions doc

[jcfranco]

Description

The following CSS class map pattern is used across many components, but this is not documented in our conventions.

• https://github.com/Esri/calcite-design-system/blob/main/packages/calcite-components/src/components/action/resources.ts#L1-L13
• https://github.com/Esri/calcite-design-system/blob/main/packages/calcite-components/src/components/action/action.tsx#L270-L272
• https://github.com/Esri/calcite-design-system/blob/main/packages/calcite-components/src/components/action/action.tsx#L242

Additionally, we should update it to include dynamically generating classes shown here.

Which Component

N/A

Resources

No response

[github-actions[bot]]

Installed and assigned for verification.

[geospatialem]

Verified in the convention readme.