Render meta tags for sources

[diegodewilde]

Describe the feature

Currently it's possible to add meta tags to sources in the .yml file, but they aren't rendered in dbt docs.
This feature is currently available for tables (see this mr).

Describe alternatives you've considered

N/A

Additional context

Not database specific.

Who will this benefit?

This will be beneficial for everyone that wants to add additional meta tags for their sources (equally to the functionality for tables).

Are you interested in contributing this feature?

Yes, I will try to contribute. ☺️