Better error for async middleware

[macdonst]

If you accidentally set a synchronous function as one of your middleware steps an error will be thrown.

Oops, something went wrong
TypeError: Cannot destructure property 'content-type' of 'state.headers' as it is undefined.
    at Object.api (file:///Users/simonmacdonald/Developer/macdonst/js-quiz/node_modules/@enhance/arc-plugin-enhance/src/http/any-catchall/router.mjs:236:31)
    at async lambda (/Users/simonmacdonald/Developer/macdonst/js-quiz/node_modules/@architect/functions/src/http/index.js:37:22)

Which is not very helpful.

With this change the error changes to:

Lambda error
Error: Error: Middleware function "isAdmin" for "/admin/" is not an async function. All middleware functions must be "async".
Lambda: @http any /*
Source: /Users/simonmacdonald/Developer/macdonst/js-quiz/node_modules/@enhance/arc-plugin-enhance/src/http/any-catchall
: Middleware function "isAdmin" for "/admin/" is not an async function. All middleware functions must be "async".

Stack trace:
Error: Middleware function "isAdmin" for "/admin/" is not an async function. All middleware functions must be "async".,    at file:///Users/simonmacdonald/Developer/macdonst/js-quiz/node_modules/@enhance/arc-plugin-enhance/src/http/any-catchall/router.mjs:95:17,    at Array.forEach (),    at Object.api (file:///Users/simonmacdonald/Developer/macdonst/js-quiz/node_modules/@enhance/arc-plugin-enhance/src/http/any-catchall/router.mjs:93:14),    at async lambda (/Users/simonmacdonald/Developer/macdonst/js-quiz/node_modules/@architect/functions/src/http/index.js:37:22)

So more descriptive and should help folks find their error quickly.