Added CLI11 library via gitmodule

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "external/CLI11"]
+	path = external/CLI11
+	url = https://github.com/CLIUtils/CLI11.git

CMakeLists.txt

@@ -5,7 +5,12 @@ project(SpotifyDownloader LANGUAGES CXX)
 set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_CXX_EXTENSIONS OFF)
+set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 
 add_executable(spotify-downloader
     src/main.cpp
 )
+
+add_subdirectory(external/CLI11)
+
+target_link_libraries(spotify-downloader PRIVATE CLI11::CLI11)

src/main.cpp

@@ -1,7 +1,19 @@
-#include <iostream>
-#include <ostream>
 
-int main(int argc, char *argv[]) {
+#include <CLI/CLI.hpp>
-  std::cout << "Hello, World" << std::endl;
+#include <iostream>
+#include <string>
+int main(int argc, char **argv) {
+  CLI::App app{"Spotify Downloader"};
+
+  std::string url;
+
+  app.add_option("-u,--url", url, "Spotify item URL");
+
+  CLI11_PARSE(app, argc, argv);
+
+  if (!url.empty()) {
+    std::cout << "Target URL: " << url << "\n";
+  }
+
   return 0;
 }