Added unicode support

Replaced strings with rune-slices, which capture unicode codepoints more
accurately.

matching.go

@@ -81,7 +81,7 @@ func pruneIndices(indices []MatchIndex) []MatchIndex {
 
 // findAllMatches tries to find all matches of the regex represented by given start-state, with
 // the given string
-func findAllMatches(start *State, str string) []MatchIndex {
+func findAllMatches(start *State, str []rune) []MatchIndex {
 	idx := 0
 	var matchFound bool
 	var matchIdx MatchIndex
@@ -104,7 +104,7 @@ func findAllMatches(start *State, str string) []MatchIndex {
 // the next search should start from.
 //
 //	Might return duplicates or overlapping indices, so care must be taken to prune the resulting array.
-func findAllMatchesHelper(start *State, str string, offset int) (bool, MatchIndex, int) {
+func findAllMatchesHelper(start *State, str []rune, offset int) (bool, MatchIndex, int) {
 	// Base case - exit if offset exceeds string's length
 	if offset > len(str) {
 		// The first value here shouldn't be used, because we should exit when the second return value is > than len(str)