Dependency checking has now fewer lines

and added 'fzf' to dependency checking process. If user doesn't have
one of the dependencies, the script terminates with an error code (1)
and error message prints to stderr.

 fontpreview | 19 +++++++------------
 1 file changed, 7 insertions(+), 12 deletions(-)

diff --git a/fontpreview b/fontpreview
index ed4e373..40cb8bc 100755
--- a/fontpreview
+++ b/fontpreview
@@ -66,18 +66,13 @@ generate_preview(){
 
 main(){
     # Checkig if needed dependencies are installed
-    type -p xdotool &>/dev/null || {
-        echo "error: Could not find 'xdotool', is it installed?"
-        return
-    }
-    type -p sxiv &>/dev/null || {
-        echo "error: Could not find 'sxiv', is it installed?"
-        return
-    }
-    type -p convert &>/dev/null || {
-        echo "error: Could not find 'imagemagick', is it installed?"
-        return
-    }
+    dependencies=(xdotool sxiv convert fzf)
+    for dependency in "${dependencies[@]}"; do
+        type -p "$dependency" &>/dev/null || {
+            echo "error: Could not find '${dependency}', is it installed?" >&2
+            exit 1
+        }
+    done
 
     # Checking for enviornment variables which the user might have set.
     # This config file for fontpreview is pretty much the bashrc, zshrc, etc