fix: Show tasks completion on document list items (#2342)

Co-authored-by: Tom Moor <tom.moor@gmail.com>

shared/utils/getTasks.js

@@ -0,0 +1,21 @@
+// @flow
+
+const CHECKBOX_REGEX = /\[(X|\s|_|-)\]\s(.*)?/gi;
+
+export default function getTasks(text: string) {
+  const matches = [...text.matchAll(CHECKBOX_REGEX)];
+  let total = matches.length;
+  if (!total) {
+    return {
+      completed: 0,
+      total: 0,
+    };
+  } else {
+    const notCompleted = matches.reduce(
+      (accumulator, match) =>
+        match[1] === " " ? accumulator + 1 : accumulator,
+      0
+    );
+    return { completed: total - notCompleted, total };
+  }
+}