[RFC] new top-level website nav item "about" #13575

I feel our website lacks a proper resource for folks who don't know what MNE-Python is/does.
I'm thinking about funders, maintainers of other software packages, students wondering if we'd be a good GSoC project, etc. Here are the pages I'd put in there:

• Overview (new page)
• Governance (currently in "Development" section)
• Changelog (currently in "Development" section)
• Bibliography (currently an orphan page)
• How to cite MNE (currently in "Documentation" section)
• Papers citing MNE (currently in "Documentation" section)

Here's some sample draft text for the new "overview" page (the links aren't live, just there to indicate which ones would be links):

About MNE-Python
MNE-Python is software for analysis and visualization of human neuroscience data.
The core package emphasizes EEG and MEG modalities, but extension packages provide enhanced support for fNIRS and EMG. Other extensions provide advanced algorithms for connectivity analysis, compatibility with BIDS, integration with LSL for real-time data streams, denoising, and many other functionalities. All software in the MNE-tools organization is open-source and permissively licensed.

mission
The mission of the MNE-Tools organization is to support neuroscience research and its application to clinical and commercial uses. This includes our software tools, but also many forms of user support and education: tutorial resources, a Q&A forum, office hours, workshops, and hackathons.

governance
The MNE project is led by a steering council, with guidance from an advisory board. Software development is overseen by the maintainer team, with many contributions from our community of users. There are also a few working groups focused on particular topics.