Normalize char before pattern lookup (#4252)

There is an edge-case in FuzzyMatchV1 during backward scan, related to
normalization: if string is initially denormalized (e.g. Unicode symbol),
backward scan will proceed further to the next char; however, when the
score is computed, the string is normalized first, then scanned based on
the pattern. This leads to accessing pattern index increment, which
itself leads to out-of-bound index access, resulting in a panic.

To illustrate the process, here's the sequence of operations when search
is perfored:

1. during backward scan by "minim" pattern

```
xxxxx Minímal example
      ^^^^^^^^^^^^
      ||||||||||||
      miniiiiiiiim <- compute score for this substring
```
2. during compute score by "minim" pattern
```
      Minímal exam
      minimal exam <- normalize chars before computing the score
      ^^^^^^
      ||||||
      minim <- at this point the pattern is already fully scanned and index
              is out-of-the-bound
```

In this commit the char is normalized during backward scan, to detect
properly the boundaries for the pattern.

src/algo/algo.go

@@ -767,6 +767,9 @@ func FuzzyMatchV1(caseSensitive bool, normalize bool, forward bool, text *util.C
 					char = unicode.To(unicode.LowerCase, char)
 				}
 			}
+			if normalize {
+				char = normalizeRune(char)
+			}
 
 			pidx_ := indexAt(pidx, lenPattern, forward)
 			pchar := pattern[pidx_]