Add Open Ephys GUI sustainability roadmap

[kabilar]

• [x] Add Open Ephys GUI sustainability roadmap which was approved by Josh Siegle
• [x] Add MkDocs Extension MagicLink to render bare URLs as links
• [x] Add MkDocs Extension TaskList to render checkboxes, as shown below:
• [x] Remove old DataJoint logos and add new logo to each partner page
• [x] Update logo sizes in each partner page
• [x] Update CSS to render images inline, as shown below:
• [x] Fix subheading in DANDI partner page

[kabilar]

Thanks @CBroz1! I have implemented your suggestions.