feat: Add folder title matching and parsing (#2067)

This is a breaking change for users of the [experimental 'folder'
functionality](https://card.camera/#/configuration/folders).

Related: #1748

src/utils/regexp-extract.ts

@@ -0,0 +1,22 @@
+/**
+ * Extracts a substring from a string using a regular expression pattern, if
+ * groupName / groupNumber is specified but not found in the result, the full
+ * match is returned.
+ */
+export const regexpExtract = (
+  pattern: string | RegExp,
+  val: string,
+  options?: {
+    groupName?: string;
+    groupNumber?: number;
+  },
+): string | null => {
+  const match = val.match(pattern);
+  if (options?.groupName && match?.groups?.[options.groupName]) {
+    return match.groups[options.groupName];
+  }
+  if (options?.groupNumber !== undefined && match?.[options.groupNumber]) {
+    return match[options.groupNumber];
+  }
+  return match ? match[0] : null;
+};