Cleanup the README.md file

[abetusk]

The README.md looks, to me at least, disorganized and hard to navigate.

I propose the following cleanup:

• Provide a graphic of the OSHW certification under the "Certification Mark Generate" that will redirect to the certification-mark-generate page (using the default certification graphic should do)
• Change all fully qualified links to shorter links without the https and in front of them
• Provide graphics under the "Pregenerated" section in addition to the links that link to the same svg as the links
• Change the link the template fact sheet (svg) links to the fact generation page (that is certification-mark-generator/facts)
• Each of the headers should link to the thing they describe. That is the "Certification Mark Generator" should link to the certification mark generator page, the "Open Hardware Facts" header should be changed to link directly to the fact generator page.
• The "Open Hardware Facts" header should be changed to be the same size as the "Open Hardware Facts"

The principle behind each of the these suggestions is "least surprise". Graphics should link to either the page they're describing or the actual graphic they're showing. Fully qualified links distracts from the place they're linking to.

I find myself coming to this page for the "Open Hardware Facts" generation page more than the "Certification Mark Generator" as I have projects that I want to document but not necessarily create OSHW certifications for. There is one link nestled in among the others that actually redirects to the "facts" page with two of the three linking to something superfluous under the "Open Hardware Facts" section.