Document env vars

doc/man/_options.txt

@@ -12,8 +12,8 @@
 
 -w, --password=password
   The documents password. If multiple documents are opened at once, the
-  password will be  used for the first one and zathura will ask for the
-  passwords of the remaining files if needed .
+  password will be used for the first one and zathura will ask for the
+  passwords of the remaining files if needed.
 
 -P, --page=number
   Opens the document at the given page number. Pages are numbered starting

doc/man/zathura.1.rst

@@ -16,6 +16,11 @@ Options
 
 .. include:: _options.txt
 
+Environment variables
+---------------------
+
+.. include:: _env.txt
+
 Mouse and key bindings
 ----------------------