fix: sass warnings when using deprecated str- mixins (#1109)

core-bootstrap/src/scss/_functions.scss

@@ -1,11 +1,13 @@
+@use 'sass:string';
+
 /**
 * Utility function to replace a substring as Sass doesn't provide the built-in method to do it
 */
 @function str-replace($string, $search, $replace: '') {
-	$index: str-index($string, $search);
+	$index: string.index($string, $search);
 
 	@if $index {
-		@return str-slice($string, 1, $index - 1) + $replace + str-replace(str-slice($string, $index + str-length($search)), $search, $replace);
+		@return string.slice($string, 1, $index - 1) + $replace + str-replace(string.slice($string, $index + string.length($search)), $search, $replace);
 	}
 
 	@return $string;
@@ -19,11 +21,11 @@ $escaped-characters: (('<', '%3c'), ('>', '%3e'), ('#', '%23'), ('(', '%28'), ('
 * ref: https://github.com/twbs/bootstrap/blob/cacbdc680ecdfee5f0c7fbb876ad15188eaf697d/scss/_functions.scss#L131
 */
 @function escape-svg($string) {
-	@if str-index($string, 'data:image/svg+xml') {
+	@if string.index($string, 'data:image/svg+xml') {
 		@each $char, $encoded in $escaped-characters {
 			// Do not escape the url brackets
-			@if str-index($string, 'url(') == 1 {
-				$string: url('#{str-replace(str-slice($string, 6, -3), $char, $encoded)}');
+			@if string.index($string, 'url(') == 1 {
+				$string: url('#{str-replace(string.slice($string, 6, -3), $char, $encoded)}');
 			} @else {
 				$string: str-replace($string, $char, $encoded);
 			}