📝 Add README

README.md

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+# go-promises
+
+Return promises from Go WASM.
+
+## Usage
+
+Write some go code, like this.
+
+```go
+import (
+    "syscall/js"
+
+    promises "codeberg.org/danjones000/go-promises"
+)
+
+func Add(a, b int) int {
+    return a + b
+}
+
+func AddWrapper() value.JSWrapper {
+    return func(this js.Value, args []js.Value) (any, error) {
+		if len(args) < 2 {
+			return nil, errors.New("add called with too few arguments")
+		}
+		a := args[0]
+		b := args[1]
+
+		if a.Type() != js.TypeNumber {
+			return nil, fmt.Errorf("First argument must be a number. %s given", a.Type())
+		}
+
+		if b.Type() != js.TypeNumber {
+			return nil, fmt.Errorf("secong argument must be a number. %s given", b.Type())
+		}
+
+        return Add(a.Int(), b.Int()), nil
+    }
+}
+
+func main() {
+    js.Global().Set("add", promises.PromisifyGoFunc(AddWrapper()))
+	<-make(chan struct{})
+}
+```
+
+Next, compile this code:
+
+```shell
+GOOS=js GOARCH=wasm go build -o ./app.wasm ./
+```
+
+Copy the `app.wasm` file, as well as the `wasm_exec.js` from your go installation, into wherever you have your web files located.
+
+```shell
+cp app.wasm "$(go env GOROOT)"/misc/wasm/wasm_exec.js path/to/web/
+```
+
+Finally, you'll need some frontend code like this:
+
+```javascript
+const go = new Go();
+WebAssembly.instantiateStreaming(fetch("app.wasm"), go.importObject).then((result) => {
+    go.run(result.instance);
+});
+```
+
+Now, the "add" function is available anywhere in your javascript.
+
+## Roadmap
+
+- [ ] Argument validation, so you can write less code in your wrapper function.
+- [ ] An easy method for attaching functions to other objects, so they don't have to be in the global scope