add comment to act hacky emit

Author: Freymaurer

src/Vitest.ReactTestingLibrary/Library.fs

@@ -340,7 +340,8 @@ type RTL =
     static member cleanup () : unit = jsNative
 
     [<ImportMember("@testing-library/react")>]
-    // [<Emit("new Promise((resolve, reject) => { $0(async () => { await $1(); resolve() }) })")>]
+    // Note: Why this emit? Fable.Promise `do!` will call a `_.then(...)` after resolving the promise, this will throw an error with the `act` function.
+    // therefore i wrap it inside another async function which will return a promise that can be awaited.
     [<Emit("(async () => await $0($1))()")>]
     static member act (actFn: unit -> Promise<unit>) : Promise<unit> = jsNative