Add JetBrains to 'Our Partners' section re sponsorship #84

[phillxnet]

With permission, we add the requested JetBrains logo to the indicated home page subsection. Following on from a recent two "All Products Pack" Licenses award to "The Rockstor Project".

Fixes #84

Includes:

• Transition 'Our Partner' logo images from static files to assets/images, enabling our use of Hugo's image pre-processors. Allowing us, in this case, to 'Fit' logo images as needed.

We still have an image size sensitivity here but this helps a little with being more robust to differing sizes and formats. Note that a future improvement could be to add a resize step to normalise all logos before fitting them.

[phillxnet]

A before and after rendering in Firefox is as follows: