Add Auto discovery

[Mirodin]

Adding MQTT auto discovery: #1315

Some keys were renamed/dropped from the initial proposal arendst/Tasmota#9267:

{
  "bd":"8.4.0.2",                                   // Tasmota SW build version - now sw
  "bt":[0,0,0,0],                                   // Buttons, 0: disabled: 1: enabled - now btn
  "id":"49A3BC",                                    // ChipID
  "li":[0,0,0,0,0,0,0,0],                           // Lights, 0: disabled, 1: Enabled
  "of":"Offline",                                   // D_OFFLINE - now ofln
  "on":"Online",                                    // D_ONLINE - now onln
  "se":[0],                                         // Sensors, 0: disabled, 0..xx index in kHAssJsonSensorTypes (??)
  "st":["OFF","ON","TOGGLE","HOLD"],                // StateText[0..3] - now state
  "sw":[0,0,0,0,0,0,0,0],                           // Switches, 0: disabled: 1: enabled - now swc?
}

I also stumbled upon some keys that were not in the proposal but could not figure out what they are:

{
  "bat":0,                                         // battery?
  "dslp":0,
  "if":0,
  "lk":0,
  "ty":0,
  "sho":[],
  "sht":[]
  "swc":[-1,-1,-1,-1,-1,-1,-1,-1],                 // I suppose this was sw, but why -1?
  "swn":[null,null,null,null,null,null,null,null],
}

[stefanbode]

{
"bat":0, // is the device battery driven and provide % of remainign power?
"dslp":0, // is the device deep_speep configured, will change online/offline behavior in HA. device ia expected to sleep most of the time
"if":0,
"lk":0,
"ty":0,
"sho":[], // configured shutteroptions, reverse, locked,.... works with HA
"sht":[] // configured shutters. Works with HA for shutters and blinds
"swc":[-1,-1,-1,-1,-1,-1,-1,-1], // I suppose this was sw, but why -1?
"swn":[null,null,null,null,null,null,null,null],
}

[Mirodin]

Thank you for chiming in and also for confirming my assumption about "bat".
I wonder if it is considered rude to ping the participants from the feature request to help out with the remaining properties? Maybe they know about additional ones that I do not have on my devices?