Improve project_browser rendering

Problem/Motivation

In project_browser, the module suite does not render optimally.

Steps to reproduce

• Install project_browser
• In "Browse projects, search for MongoDB. It is found
• The project card only carries the default project icon, it misses the actual MongoDB branding
• Click on the project title, it opens the project popin
• At the top, default project icon again, should be MongoDB-branded, with a 512x512 image (PNG) less than 10kB
• The summary is cut because it is too long. It means it should be reworded to fit
• The carousel only shows a cropped scaled-up version of the MongoDB logo. It would be more appropriate to have page examples for the most interesting features like the request tracking in the logger, or ways to illustrate the various features of the module suite, maybe a diagram showing what the suite covers in 8.x-2.x and 3.x, etc

Proposed resolution

• Rewording / reformatting: Project Browser 2.1.5 uses the summary field of the project page, cut at 200 characters, but the current summary is empty
• Adding a logo.png. Project Browser 2.1.5 shows the project's GitLab avatar, which GitLab takes from logo.png at the root of the default branch, here 8.x-2.x. This is the only item needing a commit.
• Choosing and creating relevant screenshots for the slideshow. Each image is shown in a 5:3 frame up to 700px wide and cropped to fit, so images should be 5:3 and at least 700 × 420. The current one is 448 × 138. They are edited in the Images field of the project page
• Creating a suite diagram for the slideshow
• Possibly other things to improve on these visuals

Remaining tasks

• [ ] summary
• [ ] logo.png
• [ ] screenshots
• [ ] diagram

User interface changes

• Project page
• Project browser presentation

API changes

None.

Data model changes

None.