examples: make the vweb_assets.v example more robust (always change work folder to the folder of the executable). Document the vweb.Context.handle_static behaviour.

examples/vweb/vweb_assets/vweb_assets.v

@@ -1,5 +1,6 @@
 module main
 
+import os
 import vweb
 // import vweb.assets
 import time
@@ -16,6 +17,7 @@ fn main() {
 	mut app := &App{}
 	app.serve_static('/favicon.ico', 'favicon.ico')
 	// Automatically make available known static mime types found in given directory.
+	os.chdir(os.dir(os.executable())) ?
 	app.handle_static('assets', true)
 	vweb.run(app, port)
 }

vlib/vweb/vweb.v

@@ -628,8 +628,14 @@ fn (mut ctx Context) scan_static_directory(directory_path string, mount_path str
 	}
 }
 
-// Handles a directory static
+// handle_static is used to mark a folder (relative to the current working folder)
+// as one that contains only static resources (css files, images etc).
 // If `root` is set the mount path for the dir will be in '/'
+// Usage:
+// ```v
+// os.chdir( os.executable() ) ?
+// app.handle_static('assets', true)
+// ```
 pub fn (mut ctx Context) handle_static(directory_path string, root bool) bool {
 	if ctx.done || !os.exists(directory_path) {
 		return false