Add comments to dfa's

src/parser3.h

@@ -16,6 +16,11 @@
 
 namespace parser3 {
 
+// See https://gist.github.com/pervognsen/218ea17743e1442e59bb60d29b1aa725 for
+// an explanation of this cycle/byte dfa implementation.
+//
+// Recognizes json number syntax. As a regex:
+// -?([0-9]|[1-9][0-9]*)(\.[0-9]+)?((e|E)(-|\+)?[0-9]+)?
 struct NumDfa {
   constexpr static uint64_t num_dfa_table[256] = {
       0x0ull,
@@ -326,6 +331,8 @@ private:
   uint64_t state = 6;
 };
 
+// Recognizes sequences of valid utf8 characters except 0-0x20, double quote,
+// and backslash
 struct Utf8Dfa {
   constexpr static uint64_t num_dfa_table[256] = {
       0x0ull,