Fix ReSpec warnings on GitHub spec

[igrigorik]

https://w3c.github.io/navigation-timing/

[igrigorik]

• There is a lot of unnecessary duplication of link-for's and other markup in this spec. I'm sure there is gotta be a better way to handle this.
• We should add dependencies section, similar to what we've done in other specs — that should address Please fix at least your broken links, if you want anyone to ever make any sense of your specs #65.
• Not sure on how to link PerformanceResourceTiming definition in IDL? See IDL should xref PerformanceResourceTiming #64.

@marcoscaceres @siusin was hoping to get to this over the weekend, alas.. looks like that's not going to happen and I'm away for next ~4 weeks. Any chance you could pick this one up?

[marcoscaceres]

Will take a look. No TPAC? 😭

[igrigorik]

@marcoscaceres I'm there (well, here.. since I'm sitting in our room already :)) today! Hope to see you in person today.

[marcoscaceres]

Ok, yeah... we got a lot of work to do on this one... needs quite a rewrite. We should just start by tidying it up.

Then we should do one section at a time.

@siusin, could we work on this together?

[siusin]

@marcoscaceres
Of course! There are lots of broken links to the Resource-Timing spec in the NT spec, we might need to fix the RT spec first :S