[wpigui] Add OpenURL (#4273)

This function opens a URL using the default browser.

wpigui/src/main/native/cpp/wpigui_openurl.cpp

@@ -0,0 +1,28 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#include "wpigui_openurl.h"
+
+#if _WIN32
+#ifndef WIN32_LEAN_AND_MEAN
+#define WIN32_LEAN_AND_MEAN 1
+#endif
+#include <Windows.h>
+#include <shellapi.h>
+#else
+#include <unistd.h>
+#endif
+
+void wpi::gui::OpenURL(const std::string& url) {
+#ifdef _WIN32
+  ShellExecuteA(nullptr, "open", url.c_str(), nullptr, nullptr, SW_SHOWNORMAL);
+#else
+#ifdef __APPLE__
+  static constexpr const char* opencmd = "open";
+#else
+  static constexpr const char* opencmd = "xdg-open";
+#endif
+  execlp(opencmd, opencmd, url.c_str(), static_cast<const char*>(nullptr));
+#endif
+}