cpp-httplib: update to v0.20.0 (#6663)

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("v0.20.0", "18064587e0cc6a0d5d56d619f4cbbcaba47aa5d84d86013abbd45d95c6653866")
     add_versions("v0.19.0", "c9b9e0524666e1cd088f0874c57c1ce7c0eaa8552f9f4e15c755d5201fc8c608")
     add_versions("v0.18.7", "b7b1e9e4e77565a5a9bc95e761d5df3e7c0e8ca37c90fd78b1b031bc6cb90fc1")
     add_versions("v0.18.6", "8900747bba3dda8007f1876175be699036e09e4a25ceeab51196d9365bf1993a")