Feat: Add custom scroll amount (#966)

* Added slower scroll amount mousewheel like feel

* Added custom scroll amount slider

* Made changes as requested

public/locales/en.json

@@ -466,6 +466,7 @@
       "stopped": "Stopped",
       "success": "Success",
       "system": "System",
+      "tiny": "Tiny",
       "type": "Type",
       "unknown": "Unknown",
       "username": "Username",
@@ -976,6 +977,7 @@
         "reading_mode": "Reading mode",
         "show_page_number": "Show page number",
         "skip_dup_chapters": "Skip duplicate chapters",
+        "custom_scroll_amount": "Custom scroll amount",
         "static_navigation": "Static navigation"
       },
       "overlay_mode": "Overlay mode",