Add relayinfo package and utility modules for NIP-11 support

Introduce the `relayinfo` package with `NIP-11` utilities, including `Fees`, `Limits`, and `NIPs` structures. Add utility modules for handling numbers, timestamps, and kinds. Integrate functionality for fetching and managing relay information.

pkg/protocol/relayinfo/nip11_test.go

@@ -0,0 +1,15 @@
+package relayinfo
+
+import "testing"
+
+func TestAddSupportedNIP(t *testing.T) {
+	info := NewInfo(nil)
+	info.AddNIPs(12, 12, 13, 1, 12, 44, 2, 13, 2, 13, 0, 17, 19, 1, 18)
+	for i, v := range []int{0, 1, 2, 12, 13, 17, 18, 19, 44} {
+		if !info.HasNIP(v) {
+			t.Errorf("expected info.nips[%d] to equal %v, got %v",
+				i, v, info.Nips)
+			return
+		}
+	}
+}