fix(import/utils.handleH1): fix stripping of all <h1> tags that match title

now it will only strip the very first tag that if it matches the title,
otherwise it gets turned into a h2 tag

fixes #1016

src/services/import/utils.ts

@@ -1,10 +1,14 @@
 "use strict";
 
 function handleH1(content: string, title: string) {
+    let isFirstH1Handled = false;
+
     content = content.replace(/<h1[^>]*>([^<]*)<\/h1>/gi, (match, text) => {
-        if (title.trim() === text.trim()) {
+        if (title.trim() === text.trim() && !isFirstH1Handled) {
+            isFirstH1Handled = true;
             return ""; // remove whole H1 tag
         } else {
+            isFirstH1Handled = true;
             return `<h2>${text}</h2>`;
         }
     });