Increased sample rate

[ScalyDragon]

I tried to use it for some signal debugging and experienced that the resolution is a bit low for higher speed signals. (~600KHz) If you could increase the maximum sample rate to the theoretical limit of 4.26MSamples per second or even 7.11 with lower resolution this would help a lot. Also introducing some lines to see the time resolution would be great. After all, amazing work you've done so far, the tool is great!

[anfractuosity]

Hi, that's a good point about higher sample rates, (which are defined in https://raw.githubusercontent.com/anfractuosity/flipperscope/main/scope_app_i.h).

Currently the highest ADC sample rate should be 1/1e-6 = 1Msps. From what I recall I tried 1/0.5e-6=2Msps and had an issue, I'll have a look at this again.

Also I agree having some lines would be useful too, currently each pixel represents a single time period, so for example the time period between each pixel would be 1us, if you select 1us time period.