Adds FFT focus lens mnemonic

src/toolbox_scs/constants.py

@@ -319,6 +319,9 @@ mnemonics = {
     "PP800_FocusLens": ({'source': 'SCS_ILH_LAS/MOTOR/LT_SPARE1',
                          'key': 'actualPosition.value',
                          'dim': None},),
+    "FFT_FocusLens": ({'source': 'SCS_CDIFFT_FDM/MOTOR/BARLOW_1',
+                       'key': 'actualPosition.value',
+                       'dim': None},),
     # 1st lens of telescope (setup of August 2019)
     "PP800_TeleLens": ({'source': 'SCS_ILH_LAS/MOTOR/LT7',
                         'key': 'actualPosition.value',