Style: Harmonize header includes in platform ports

This applies our existing style guide, and adds a new rule to that style
guide for modular components such as platform ports and modules:

Includes from the platform port or module should be included with relative
paths (relative to the root folder of the modular component, e.g.
`platform/linuxbsd/`), in their own section before Godot's "core" includes.

The `api` and `export` subfolders also need to be handled as self-contained
(and thus use relative paths for their "local" includes) as they are all
compiled for each editor platform, without necessarily having the api/export
matching platform folder in the include path.
E.g. the Linux editor build will compile `platform/android/{api,export}/*.cpp`
and those need to use relative includes for it to work.

platform/web/javascript_bridge_singleton.cpp

@@ -30,9 +30,10 @@
 
 #include "api/javascript_bridge_singleton.h"
 
-#include "emscripten.h"
 #include "os_web.h"
 
+#include <emscripten.h>
+
 extern "C" {
 extern void godot_js_os_download_buffer(const uint8_t *p_buf, int p_buf_size, const char *p_name, const char *p_mime);
 }
@@ -352,6 +353,7 @@ Variant JavaScriptBridge::eval(const String &p_code, bool p_use_global_exec_cont
 			return Variant();
 	}
 }
+
 #endif // JAVASCRIPT_EVAL_ENABLED
 
 void JavaScriptBridge::download_buffer(Vector<uint8_t> p_arr, const String &p_name, const String &p_mime) {