api: quality options for screen mirroring (#313)

## Link to GitHub Issue, if one exists
n/a

## Description of change
Allow the server to override client's quality options for screen
mirroring.

On Windows / Android versions (flutter-based) clients, this is already
in the options of those apps. However, the iOS version lacks the quality
options.

## Testing
Tested with iOS and Windows clients.

src/spice2x/api/modules/capture.h

@@ -1,10 +1,15 @@
 #pragma once
 
+#include <optional>
+
 #include "api/module.h"
 #include "api/request.h"
 
 namespace api::modules {
 
+    extern std::optional<uint32_t> CAPTURE_QUALITY;
+    extern std::optional<uint32_t> CAPTURE_DIVIDE;
+
     class Capture : public Module {
     public:
         Capture();