docs update

Updated some docs stuff

docs/objects/Program/onError.md

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+# onError
+
+`onError(self, err)`<br>
+This is a custom event which gets triggered as soon as the program catched a error.
+
+Here is a example on how to add a onError event to your program:
+
+```lua
+local basalt = require("basalt")
+
+local main = basalt.createFrame()
+local aProgram = main:addProgram():execute("rom/programs/shell.lua")
+
+local function onProgramError(self, err)
+local errFrame = main:addFrame()
+    :setSize(30, 10)
+    :setPosition("parent.w / 2 - self.w / 2", "parent.h / 2 - self.h / 2")
+
+errFrame:addLabel()
+    :setPosition(2, 3)
+    :setSize("parent.w - 2", "parent.h - 3")
+    :setText(err)
+
+errFrame:addButton()
+    :setPosition("parent.w", 1)
+    :setSize(1, 1)
+    :setText("X")
+    :onClick(function()
+        errFrame:remove()
+    end)
+end
+
+aProgram:onError(onProgramError)
+```