chore(h264): comment to explain boundary split

if Annex B boundary cuts off b/w packets, explain how it'll be handled

src/codec/h264.rs

@@ -90,6 +90,9 @@ impl NalParser {
         let mut did_find_boundary = false;
 
         for (idx, byte) in data.iter().enumerate() {
+            // If the current FU-A has a boundary that splits at end, ignore the last or
+            // last two zeros because this boundary will be handled when the start of
+            // next packet is being read, and these zeros will be removed on walk-back.
             if byte == &0x00 && idx + 2 < data.len() && &data[idx..idx + 3] == &[0x00; 3] {
                 debug!("Found boundary with index range: {} - {}.", idx, idx + 2);
                 // we found a boundary, let NalParser know that it should now keep adding