chore: remove outdated extension thumbnails

src/extensions/outliner/mod.json

@@ -3,7 +3,6 @@
   "version": "0.5.0",
   "id": "87e077cc-5402-451c-ac70-27cc4ae65546",
   "description": "Adds a table of contents to the side panel to overview and navigate the current page's headings and subheadings.",
-  "thumbnail": "outliner.png",
   "tags": ["panel"],
   "authors": [
     {

src/extensions/scroller/mod.json

@@ -3,7 +3,6 @@
   "version": "0.4.0",
   "id": "0a958f5a-17c5-48b5-8713-16190cae1959",
   "description": "Adds buttons to pages and full-page calendars to jump across content easily.",
-  "thumbnail": "scroller.png",
   "tags": ["scroll-to-top", "scroll-to-bottom", "calendar-scroll"],
   "authors": [
     {

src/extensions/topbar/mod.json

@@ -3,7 +3,6 @@
   "version": "0.4.0",
   "id": "e0700ce3-a9ae-45f5-92e5-610ded0e348d",
   "description": "Customise the Notion interface's topbar and add an always on top toggle to the window in-app.",
-  "thumbnail": "topbar.jpg",
   "tags": ["topbar-icons", "always-on-top"],
   "authors": [
     {

src/extensions/word-counter/mod.json

@@ -3,7 +3,6 @@
   "version": "0.4.0",
   "id": "b99deb52-6955-43d2-a53b-a31540cd19a5",
   "description": "Adds word, character, sentence and block counts with average reading and speaking times to the panel.",
-  "thumbnail": "word-counter.jpg",
   "tags": ["panel"],
   "authors": [
     {