added subghz-playlist to main application menu

applications/main/sub_playlist/playlist_file.c

@@ -0,0 +1,21 @@
+#include <furi.h>
+
+#include <storage/storage.h>
+#include <flipper_format/flipper_format_i.h>
+
+int playlist_count_playlist_items(Storage* storage, const char* file_path) {
+    FlipperFormat* format = flipper_format_file_alloc(storage);
+    if(!flipper_format_file_open_existing(format, file_path)) {
+        return -1;
+    }
+    int count = 0;
+    FuriString* data;
+    data = furi_string_alloc();
+    while(flipper_format_read_string(format, "sub", data)) {
+        ++count;
+    }
+    flipper_format_file_close(format);
+    flipper_format_free(format);
+    furi_string_free(data);
+    return count;
+}