docs: clarify on navigation

README.md

@@ -7,6 +7,9 @@ Startify basically provides two things:
    it reads from STDIN), startify will show a small but pretty start screen
    which shows recently used files and sessions by default.
 
+   You can either navigate to a certain menu entry or you just key in whatever
+   is written between the square brackets on that line.
+
 2) It eases handling of loading and saving sessions by only working with a
    certain directory. Two commands are used for convenience:
 

doc/startify.txt

@@ -40,6 +40,9 @@ Startify basically provides two things:
    it reads from STDIN), startify will show a small but pretty start screen
    which shows recently used files and sessions by default.
 
+   You can either navigate to a certain menu entry or you just key in whatever
+   is written between the square brackets on that line.
+
 2) It eases handling of loading and saving sessions by only working with a
    certain directory. Two commands are used for convenience: