Add source maps configuration

[ertrzyiks]

This change let us configure rollbar js to use source maps https://rollbar.com/docs/guides_sourcemaps/

Example

ftrrtf_rollbar:
    client:
        access_token: "%rollbar_client_access_token%"
        source_map_enabled: true
        code_version: '%version%'

[ftrrtf]

:+1: