Update default script to export function as we are now using deno to execute functions

constants.py

@@ -1,6 +1,6 @@
 DEFAULT_FUNCTION_NAME = 'foo'
 
-DEFAULT_SCRIPT = """async (req) => {
+DEFAULT_SCRIPT = """export default async (req) => {
     console.log(`Method:${req.method}`)
     console.log(`Generating ${environment.lines} random lines...`)
     let svgContent = "";