Add TCH/H decoder block with AMR multirate support

Add new TCHH channel mode
Add two new optional arguments

    -m CHAN_MODE, --mode=CHAN_MODE
                        Channel mode. Valid options are 'BCCH' (Non-combined
                        C0), 'BCCH_SDCCH4'(Combined C0), 'SDCCH8' (Stand-alone
                        control channel) 'TCHF' (Traffic Channel, Full rate),
                        'TCHH' (Traffic Channel, Half rate)

    --sub-channel=TCH_H_CHANNEL
                        TCH/H sub-channel. [default=0]
    --multi-rate=MULTI_RATE
                        The MultiRrate configuration element from the
                        Assigment Command message. Example: 28111a40. See 3GPP
                        TS 44.018 - 10.5.2.21aa MultiRate configuration

Example:
    grgsm_decode -m TCHH --sub-channel 0 --multi-rate 2811 -o voice.amr ...
diff --git a/include/grgsm/decoding/tch_f_decoder.h b/include/grgsm/decoding/tch_f_decoder.h
index df5f0ff..ae65f06 100644
--- a/include/grgsm/decoding/tch_f_decoder.h
+++ b/include/grgsm/decoding/tch_f_decoder.h
@@ -41,7 +41,8 @@
         TCH_AFS5_15,
         TCH_AFS4_75,
         TCH_FS,
-        TCH_EFR
+        TCH_EFR,
+        TCH_HS,
     };
 
     /*!