[feat] engines: add findfiles.net file search engine

FindFiles.net is a specialized file search engine designed to help you search
files online with precision. Unlike traditional search engines that mainly index
web pages, FindFiles focuses on finding real files on the internet - including
PDFs, documents, archives, videos, datasets, and more. [1]

[1] https://findfiles.net

searx/settings.yml

@@ -977,6 +977,34 @@ engines:
     shortcut: fd
     disabled: true
 
+  - name: findfiles
+    engine: findfiles
+    findfiles_categ: all
+    categories: files
+    shortcut: fif
+    disabled: true
+
+  - name: findfiles images
+    engine: findfiles
+    findfiles_categ: image
+    categories: images
+    shortcut: fifi
+    disabled: true
+
+  - name: findfiles videos
+    engine: findfiles
+    findfiles_categ: video
+    categories: videos
+    shortcut: fifv
+    disabled: true
+
+  - name: findfiles music
+    engine: findfiles
+    findfiles_categ: audio
+    categories: music
+    shortcut: fifm
+    disabled: true
+
   - name: findthatmeme
     engine: findthatmeme
     shortcut: ftm