Create application from config file

[geospatial-jeff]

Create a config file and a module for parsing that config file into a stac api application. The config file should allow user to specify things like backend, extensions, middleware, ports, etc. Have to decide what config language to use, some options are yaml/toml/json/hcl.

Some other examples of this in geo:

• pygeoapi (most relevant)
• tegola
• martin
• pg_tileserv