Update cpp-httplib to v0.18.3 (#6087)

packages/c/cpp-httplib/xmake.lua

@@ -7,6 +7,7 @@ package("cpp-httplib")
     set_urls("https://github.com/yhirose/cpp-httplib/archive/refs/tags/$(version).tar.gz",
              "https://github.com/yhirose/cpp-httplib.git")
 
+    add_versions("v0.18.3", "a0567bcd6c3fe5cef1b329b96245119047f876b49e06cc129a36a7a8dffe173e")
     add_versions("v0.18.1", "405abd8170f2a446fc8612ac635d0db5947c0d2e156e32603403a4496255ff00")
     add_versions("v0.17.3", "95bd6dba4241656c59d6f0854d408d14c220f7c71e673319ee27d30aee741aaa")
     add_versions("v0.17.0", "dd3ba355b6aa74b7a0bff982ad0de7af6d9672fd83af30aa84eb707974d2a903")