Adding support Anycubic i3 Mega

Definition for _Anycubic i3 Mega_ from the user manual.

resources/definitions/anycubic_i3_mega.def.json

@@ -0,0 +1,57 @@
+{
+	"version":2,
+    "name":"Anycubic i3 Mega",
+    "inherits":"fdmprinter",
+    "metadata":{
+        "visible":true,
+        "author":"TheTobby",
+        "manufacturer":"Anycubic",
+        "file_formats":"text/x-gcode",
+        "icon":"icon_ultimaker2",
+        "platform":"prusai3_platform.stl"
+    },
+    "overrides":{
+        "machine_name":{
+            "default_value":"Anycubic i3 Mega"
+        },
+        "machine_heated_bed":{
+            "default_value":true
+        },
+        "machine_width":{
+            "default_value":210
+        },
+        "machine_height":{
+            "default_value":205
+        },
+        "machine_depth":{
+            "default_value":210
+        },
+        "machine_center_is_zero":{
+            "default_value":false
+        },
+        "machine_nozzle_size":{
+            "default_value":0.4
+        },
+        "material_diameter":{
+            "default_value":1.75
+		},
+        "speed_travel":{
+            "default_value":60
+        },		
+        "speed_print":{
+            "default_value":50
+        },
+        "gantry_height":{
+            "default_value":0
+        },
+        "machine_gcode_flavor":{
+            "default_value":"RepRap (Marlin/Sprinter)"
+        },
+        "machine_start_gcode":{
+            "default_value":"G21 ;metric values\nG90 ;absolute positioning\nM82 ;set extruder to absolute mode\nM107 ;start with the fan off\nG28 X0 Y0 ;move X/Y to min endstops\nG28 Z0 ;move Z to min endstops\nG1 Z15.0 F{travel_speed} ;move the platform down 15mm\nG92 E0 ;zero the extruded length\nG1 F200 E3 ;extrude 3mm of feed stock\nG92 E0 ;zero the extruded length again\nG1 F{travel_speed}\nM117 Printing...\nG5"
+        },
+        "machine_end_gcode":{
+            "default_value":"M104 S0 ; turn off extruder\nM140 S0 ; turn off bed\nM84 ; disable motors\nM107\nG91 ;relative positioning\nG1 E-1 F300 ;retract the filament a bit before lifting the nozzle\nto release some of the pressure\nG1 Z+0.5 E-5 ;X-20 Y-20 F{travel_speed} ;move Z up a bit and retract filament even more\nG28 X0 ;Y0 ;move X/Y to min endstops\nso the head is out of the way\nG1 Y180 F2000\nM84 ;steppers off\nG90\nM300 P300 S4000"
+        }
+    }
+}