audio/shortwave: add dependency for saving recent songs

$ GST_DEBUG=2 shortwave
[...]
WARN GST_ELEMENT_FACTORY gstelementfactory.c:462:GstElement *gst_element_factory_make(const gchar *, const gchar *): no such element factory "vorbisenc"!
ERROR GST_PIPELINE grammar.y:816:int priv_gst_parse_yyparse(void *, graph_t *): no element "vorbisenc"
ERROR GST_PIPELINE grammar.y:901:int priv_gst_parse_yyparse(void *, graph_t *): link has no sink [source=@0x808b72a40]
WARN GST_ELEMENT_FACTORY gstelementfactory.c:462:GstElement *gst_element_factory_make(const gchar *, const gchar *): no such element factory "oggmux"!
ERROR GST_PIPELINE grammar.y:816:int priv_gst_parse_yyparse(void *, graph_t *): no element "oggmux"
ERROR GST_PIPELINE grammar.y:901:int priv_gst_parse_yyparse(void *, graph_t *): link has no source [sink=@0x0]
ERROR GST_PIPELINE grammar.y:901:int priv_gst_parse_yyparse(void *, graph_t *): link has no source [sink=@0x815386af0]
thread 'main' panicked at 'Unable to create recorderbin: Error { domain: gst_parse_error, code: 1, message: "no element \"vorbisenc\"" }', src/audio/backend/gstreamer_backend.rs:301:84