title: Reactive accumulation of data coming in bursts
body: <p>The problem: there is a stream of numeric values. Values are pushed in bursts so 100 values can come very close to each other (time-wise) say each 5-10 ms and then it possibly stops for a while, then can burst again.The idea is to show accumulated value (sum) of windows of at most length of 500 ms.</p>
  
  <p>My first attempt was with Buffer(500ms) but this is causing constant pumping of events (every 500 ms) with the sum of 0 (as the accumulated buffer items os 0), it could be fixed with filtering by empty buffers but I would really like to avoid that entirely and only open the buffering after a value is actually pushed after a period of "silence".</p>
  
  <p>Additional restrictions: the implementation is UniRx which does not contain all the Rx operators, notably Window (which I suspect could be useful in that case) so solution is limited to basic operators including Buffer.</p>