std: add std.http.Headers field

Based on lua-http's data structure

Author: daurnimator

CMakeLists.txt

@@ -521,6 +521,8 @@ set(ZIG_STD_FILES
     "hash/siphash.zig"
     "hash_map.zig"
     "heap.zig"
+    "http.zig"
+    "http/headers.zig"
     "io.zig"
     "io/c_out_stream.zig"
     "io/seekable_stream.zig"

std/http.zig

@@ -0,0 +1,5 @@
+test "std.http" {
+    _ = @import("http/headers.zig");
+}
+
+pub const Headers = @import("http/headers.zig").Headers;