Add userid example functions

userids_examples_test.go

@@ -0,0 +1,27 @@
+package gomatrix
+
+import "fmt"
+
+func ExampleEncodeUserLocalpart() {
+	localpart := EncodeUserLocalpart("Alph@Bet_50up")
+	fmt.Println(localpart)
+	// Output: _alph=40_bet__50up
+}
+
+func ExampleDecodeUserLocalpart() {
+	localpart, err := DecodeUserLocalpart("_alph=40_bet__50up")
+	if err != nil {
+		panic(err)
+	}
+	fmt.Println(localpart)
+	// Output: Alph@Bet_50up
+}
+
+func ExampleExtractUserLocalpart() {
+	localpart, err := ExtractUserLocalpart("@alice:matrix.org")
+	if err != nil {
+		panic(err)
+	}
+	fmt.Println(localpart)
+	// Output: alice
+}