Add a link to a CM5 testpoints visualisation

[KoviRobi]

I wanted to use the UART testpoints (accidentally torn off the JST header I soldered, by trying to unplug the connector), and it was hard to know which one is which.

Thought it might be useful for others, feel free to just vendor the SVG or otherwise request changes (including license changes or repo moves). It's more or less just a scatter plot example using the table from the schematic PDF plus a photo. But might be useful for others.

[katshann-raspberry]

@KoviRobi Thanks for this suggested contribution. I'll check with our subject matter experts about whether and how to include this information.
Looking at your SVG in Chrome, there's some superposition of text:

Fine in Firefox though.

ETA: I'm inclined to think that we might instead put a diagram of this nature in https://pip.raspberrypi.com/documents/RP-008180-DS-6 Appendix A, rather than the HTML docs.

[KoviRobi]

Ah thanks for checking, turns out while the dominant-baseline attribute itself is widely supported, the values I used (text-bottom and text-top) aren't. Fixed using the dy attribute instead.

And yes I'd be very happy with a direct image in the PDF (as long as it is searchable/not just a screenshot). I've used MIT no attribution as I think that makes it easiest to just use however but happy to change to whatever, if you just want to directly use the SVG.

But also since you have the PCB layout you could just as easily use that to generate a render of the bottom of the PCB with the testpoints labelled (probably).