[docs] Add example requests to API Reference

[brzep]

PR for #752

Added example requests to RTP/MP4/DeckLink pages to make going to HTTP Routes page not necessary.
Requests are split into two code blocks to make copying request json easier.

[WojciechBarczynski]

I think that we should emphasize in docs, that setting required to true for failable streams will stop the entire processing of the LiveCompositor once such input fails/stops sending data and avoid setting it to true in example requests.

[wkozyra95]

agree, but I don't think setting it to true is the issue here, specifying this field at all in the example is more of a problem

[WojciechBarczynski]

@brzep BTW you don't have to assign the entire team for review. Usually assigning 1 or 2 team members should be enough.

[brzep]

I know I don't have to assign everyone (normally I don't do that), but I assumed it's a very simple change and reviewing it will take like 2 minutes, so more people can do it. I think with the docs the more people see them, possibly the more feedback I'll receive so they'll be more user friendly.

[wkozyra95]

Example requests should include stuff that is required, or optional fields that most use will need to specify. Stuff like offset/required/ffmpeg_options do not help here