Put function arguments first before description

Arguments are more important and thus is makes sense to put them first so the person reading the code can get to them sooner.
FWIW I took a survey of several repos and all but one of them (of the ones that used both -a and -d flags) put the description last.
Resolves #38

functions/__fzf_display_value_or_error.fish

@@ -1,5 +1,5 @@
 # helper function for __fzf_search_shell_variables
-function __fzf_display_value_or_error --description "Displays either the value of the variable passed in, or an informative message if it is not available." --argument-names variable_name
+function __fzf_display_value_or_error --argument-names variable_name --description "Displays either the value of the variable passed in, or an informative message if it is not available."
     if set --query $variable_name
         echo $$variable_name
     else

functions/__fzf_preview_file.fish

@@ -1,5 +1,5 @@
 # helper function for __fzf_search_current_dir
-function __fzf_preview_file --description "Prints a preview for the given file based on its file type." --argument-names file_path
+function __fzf_preview_file --argument-names file_path --description "Prints a preview for the given file based on its file type."
     if test -f "$file_path" # regular file
         bat --style=numbers --color=always "$file_path"
     else if test -d "$file_path" # directory

functions/__fzf_report_file_type.fish

@@ -1,5 +1,5 @@
 # helper function for __fzf_preview_file
-function __fzf_report_file_type --description "Explain the file type for a file." --argument-names file_path file_type
+function __fzf_report_file_type --argument-names file_path file_type --description "Explain the file type for a file."
     set_color red
     echo "Cannot preview '$file_path': it is a $file_type."
     set_color normal