add required template for friend classes

README.md

@@ -201,7 +201,7 @@ Runtimes like Node.js and Cloudflare Workers use the V8 regex engine, which is s
 
 ```cpp
 // Define a regex engine that conforms to the following interface
-// For eample we will use v8 regex engine
+// For example we will use v8 regex engine
 
 class v8_regex_provider {
  public:
@@ -215,7 +215,7 @@ class v8_regex_provider {
 };
 
 // Define a URLPattern
-auto pattern = ada::parse_url_pattern<v8_regex_provider>(("/books/:id(\\d+)", "https://example.com");
+auto pattern = ada::parse_url_pattern<v8_regex_provider>("/books/:id(\\d+)", "https://example.com");
 
 // Check validity
 if (!pattern) { return EXIT_FAILURE; }

include/ada/url_pattern.h

@@ -284,7 +284,8 @@ class url_pattern {
   }
 #endif  // ADA_TESTING
 
-  friend tl::expected<url_pattern, errors> parser::parse_url_pattern_impl(
+  template <url_pattern_regex::regex_concept P>
+  friend tl::expected<url_pattern<P>, errors> parser::parse_url_pattern_impl(
       std::variant<std::string_view, url_pattern_init> input,
       const std::string_view* base_url, const url_pattern_options* options);