add catalog functionality

[andersy005]

this PR adds a few cataloging functionality via the leap-catalog command:

❯ leap-catalog --help                                                                                                                                                                                              
usage: leap-catalog [-h] {validate,generate} ...

Utilities for cataloging feedstocks for LEAP

positional arguments:
  {validate,generate}  sub-command help
    validate           Validate the feedstocks
    generate           Generate the catalog

options:
  -h, --help           show this help message and exit

one can

• validate a single feedstock/catalog.yaml via

❯ leap-catalog validate --single https://github.com/leap-stc/proto_feedstock/blob/main/feedstock/catalog.yaml                                                                                                      
✅ Valid feedstock: (1)
  📂 https://github.com/leap-stc/proto_feedstock/blob/main/feedstock/catalog.yaml

• generate a set of feedstocks and generate the consolidated-web-catalog.json via

❯ leap-catalog generate --path https://raw.githubusercontent.com/leap-stc/data-management/staging/catalog/input.yaml --output /tmp/                                                                             
['https://github.com/carbonplan/ocean-carbon-sink-data-feedstock/blob/main/feedstock/catalog.yaml']
✅ Valid feedstocks: (1)
  📂 https://github.com/carbonplan/ocean-carbon-sink-data-feedstock/blob/main/feedstock/catalog.yaml

❌ Invalid feedstocks: (0)
  🚀 None found

Catalog written to /private/tmp/output/consolidated-web-catalog.json

Cc @norlandrhagen, @jbusecke