Update component docs

druid/base/back_handler.lua

@@ -1,6 +1,14 @@
 --- Component to handle back key (android, backspace)
 -- @module druid.back_handler
 
+--- Component events
+-- @table Events
+-- @tfield druid_event on_back On back handler callback
+
+--- Component fields
+-- @table Fields
+-- @tfield any params Params to click callbacks
+
 local Event = require("druid.event")
 local const = require("druid.const")
 local component = require("druid.component")
@@ -10,11 +18,9 @@ local M = component.create("back_handler", { const.ON_INPUT })
 
 --- Component init function
 -- @function back_handler:init
--- @tparam table self Component instance
 -- @tparam callback callback On back button
 -- @tparam[opt] params Callback argument
 function M.init(self, callback, params)
-	self.callback = callback
 	self.params = params
 
 	self.on_back = Event(callback)