Add cfdm package to Frameworks sub-section

[sadielbartholomew]

Project name: cfdm (all lower case)

Project website/repository: https://github.com/NCAS-CMS/cfdm

License: MIT

Checklist for new projects:

• [x] The project is open-source and accessible.
• [x] Searched the existing entries to make sure this is not a duplicate.
• [x] Contains only a single addition (make separate PRs if adding more than one).
• [x] Added the link to the bottom of the relevant category.
• [x] Add icon from the media/icon/ folder if applicable (like ![Python](media/icon/python.png) ).
• [n/a] Created a new category only if necessary.
• [x] Checked spelling and grammar.
• [x] Removed trailing whitespace and periods.
• [they are all minuses in this list so that would be inconsistent?] Confirm the dash – is not a minus -.
• [x] Used title-casing (AP style) for project name.

Please note I'm also putting in a PR, in a moment, for a related package cf-python, as referenced in the description here. Thanks.

[sadielbartholomew]

Closing this since now since it is over two years since my post and the project/repo has clearly gone stale.