add window prompt

gleam.toml

@@ -1,5 +1,5 @@
 name = "plinth"
-version = "0.4.14"
+version = "0.4.15"
 description = "Bindings to Node.js and browser platform APIs"
 target = "javascript"
 

src/plinth/browser/window.gleam

@@ -11,6 +11,9 @@ pub fn self() -> Window
 @external(javascript, "../../window_ffi.mjs", "alert")
 pub fn alert(a: String) -> Nil
 
+@external(javascript, "../../window_ffi.mjs", "prompt")
+pub fn prompt(a: String) -> Result(String, Nil)
+
 @external(javascript, "../../window_ffi.mjs", "addEventListener")
 pub fn add_event_listener(type_: String, listener: fn(Event) -> Nil) -> Nil
 

src/window_ffi.mjs

@@ -8,6 +8,15 @@ export function alert(message) {
   window.alert(message);
 }
 
+export function prompt(message, defaultValue) {
+  let text = window.prompt(message, defaultValue);
+  if (text !== null) {
+    return new Ok(text)
+  } else {
+    return new Error()
+  }
+}
+
 export function addEventListener(type, listener) {
   return window.addEventListener(type, listener);
 }