Add info about dependencies

README.md

@@ -21,6 +21,47 @@ file manager but I believe that it can be easily integrated into
 other programs as well if they support previews provided by
 external programs like lf does.
 
+## Dependencies
+
+These programs are needed to make specific previews work.
+If a preview requires some program and it's not found on the system,
+`ctpv` will fallback to other previews.
+
+Image files:
+* `ueberzug`
+
+Videos:
+* `ffmpegthumbnailer`
+
+Text files:
+* `source-highlight`
+* `highlight`
+
+Diff files:
+* `colordiff`
+* `delta`
+* `diff-so-fancy`
+
+Markdown:
+* `mdcat`
+
+JSON files:
+* `jq`
+
+PDF files:
+* `pdftoppm`
+
+Torrent files:
+* `transmission-show`
+
+HTML files:
+* `w3m`
+* `lynx`
+* `elinks`
+
+Any other files:
+* `exiftool`
+
 ## Installation
 
 ### Manual