feat: add initial experimental Twitch Eventsub support (#5837)

Co-authored-by: nerix <nerixdev@outlook.de>

lib/twitch-eventsub-ws/src/string.cpp

@@ -0,0 +1,23 @@
+#include "twitch-eventsub-ws/string.hpp"
+
+#include <boost/json.hpp>
+#include <QString>
+
+#include <string>
+
+namespace chatterino::eventsub::lib {
+
+boost::json::result_for<String, boost::json::value>::type tag_invoke(
+    boost::json::try_value_to_tag<String> /*tag*/,
+    const boost::json::value &jvRoot)
+{
+    auto v = boost::json::try_value_to<std::string>(jvRoot);
+    if (v.has_error())
+    {
+        return v.error();
+    }
+
+    return String(std::move(v.value()));
+}
+
+}  // namespace chatterino::eventsub::lib