Remove examples/internal

Users find it frustrating that example code doesn't work out of tree.
This makes copying the examples out of the repo easier.

Relates to #1981

examples/data-channels/jsfiddle/main.go

@@ -7,11 +7,17 @@
 package main
 
 import (
+	"bufio"
+	"encoding/base64"
+	"encoding/json"
+	"errors"
 	"fmt"
+	"io"
+	"os"
+	"strings"
 	"syscall/js"
 
 	"github.com/pion/webrtc/v4"
-	"github.com/pion/webrtc/v4/examples/internal/signal"
 )
 
 func main() {
@@ -63,7 +69,7 @@ func main() {
 	})
 	pc.OnICECandidate(func(candidate *webrtc.ICECandidate) {
 		if candidate != nil {
-			encodedDescr := signal.Encode(pc.LocalDescription())
+			encodedDescr := encode(pc.LocalDescription())
 			el := getElementByID("localSessionDescription")
 			el.Set("value", encodedDescr)
 		}
@@ -94,7 +100,7 @@ func main() {
 			}
 
 			descr := webrtc.SessionDescription{}
-			signal.Decode(sd, &descr)
+			decode(sd, &descr)
 			if err := pc.SetRemoteDescription(descr); err != nil {
 				handleError(err)
 			}
@@ -146,3 +152,45 @@ func handleError(err error) {
 func getElementByID(id string) js.Value {
 	return js.Global().Get("document").Call("getElementById", id)
 }
+
+// Read from stdin until we get a newline
+func readUntilNewline() (in string) {
+	var err error
+
+	r := bufio.NewReader(os.Stdin)
+	for {
+		in, err = r.ReadString('\n')
+		if err != nil && !errors.Is(err, io.EOF) {
+			panic(err)
+		}
+
+		if in = strings.TrimSpace(in); len(in) > 0 {
+			break
+		}
+	}
+
+	fmt.Println("")
+	return
+}
+
+// JSON encode + base64 a SessionDescription
+func encode(obj *webrtc.SessionDescription) string {
+	b, err := json.Marshal(obj)
+	if err != nil {
+		panic(err)
+	}
+
+	return base64.StdEncoding.EncodeToString(b)
+}
+
+// Decode a base64 and unmarshal JSON into a SessionDescription
+func decode(in string, obj *webrtc.SessionDescription) {
+	b, err := base64.StdEncoding.DecodeString(in)
+	if err != nil {
+		panic(err)
+	}
+
+	if err = json.Unmarshal(b, obj); err != nil {
+		panic(err)
+	}
+}