Include titiler API endpoint.

[sharkinsspatial]

As this construct becomes used across several projects we should incorporate an optional titiler API endpoint (with a titiler-pgstac extension). Ideally, this would follow the same implementation pattern that we currently use for the stac-api.

[emileten]

@sharkinsspatial have you started working on this ? In MAAP we're using cdk-pgstac, and we want to use the opportunity of deployment migration to consolidate on one tiler instance that we get from a reused common resource like this. cc @abarciauskas-bgse.

[emileten]

I think we can close -- a titiler API endpoint was added in #42.