fs(3lua): init man pages

Initialise man pages for the fs module.

man/fs/fs.basename.3lua.scd

@@ -0,0 +1,29 @@
+FS.BASENAME(3lua) "3lua" "Callisto manual pages"
+
+# NAME
+*fs.basename* - get the last component of a path
+
+# SYNOPSIS
+*fs.basename*(_path_: *string*)
+
+# DESCRIPTION
+*fs.basename* returns the last component of _path_,
+removing any trailing slash "/" characters.
+If _path_ consists entirely of slash characters, the string "/" is
+returned.
+If _path_ is an empty string, the string "." is returned.
+
+This is purely a string manipulation function
+and depends on no outside state.
+
+# EXAMPLES
+Print the name of the currently running script file:
+
+	print("name of script file is " .. fs.basename(arg[0]))
+
+Output example:
+
+	assert(fs.basename("/etc/fstab") == "fstab")
+
+# SEE ALSO
+callisto(3lua), fs(3lua)