Add ability to type a space with the input keyboard by long-pressing "_" (#1550)

Co-authored-by: Mayco <tristan@polymerprints.nl>
Co-authored-by: あく <alleteam@gmail.com>

applications/gui/modules/text_input.c

@@ -131,7 +131,9 @@ static bool char_is_lowercase(char letter) {
 }
 
 static char char_to_uppercase(const char letter) {
-    if(isalpha(letter)) {
+    if(letter == '_') {
+        return 0x20;
+    } else if(isalpha(letter)) {
         return (letter - 0x20);
     } else {
         return letter;