feat(opds): Allow selecting the download format

When downloading a book via OPDS, the last acquisition link is chosen when there are multiple. This allows choosing which format to download when there are many. Having only one format will automatically download that.

src/activities/browser/OpdsFormatLabel.h

@@ -0,0 +1,13 @@
+#pragma once
+
+#include <OpdsParser.h>
+
+#include <string>
+#include <vector>
+
+const char* opdsBaseFormatLabel(const OpdsAcquisitionLink& acquisition);
+std::string opdsFormatSelectionLabel(const OpdsAcquisitionLink& acquisition,
+                                     const std::vector<OpdsAcquisitionLink>& acquisitionLinks,
+                                     const std::string& serverUrl);
+std::vector<std::string> buildOpdsFormatSelectionLabels(const std::vector<OpdsAcquisitionLink>& acquisitionLinks,
+                                                        const std::string& serverUrl);