Expanding IFS datasource pressure levels

[NickGeneva]

Earth2Studio Pull Request

Description

Improving IFS data source lexicon to include all available pressure levels based on ECMWF's documentation.

Closes: https://github.com/NVIDIA/earth2studio/issues/32

Checklist

• [x] I am familiar with the Contributing Guidelines.
• [x] New or existing tests cover these changes.
• [x] The documentation is up to date with these changes.
• [x] The CHANGELOG.md is up to date with these changes.
• [x] An issue is linked to this pull request.

Dependencies

[NickGeneva]

/blossom-ci

[NickGeneva]

/blossom-ci