Use more icons in autocomplete box

[cezarsa]

This PR changes the autocomplete dialog to use more icons, distinguishing structs, interfaces and other types.

Before:

After:

The following code is used in the autocomplete example above:

type BoolType bool
const Const = 8
func Func() {}
type Interface interface{}
type StringType string
type Struct struct{}
var Var = 9

[ramya-rao-a]

Sweet! Just curious, why use Class icon for struct and Struct icon for other types?

Also, dont forget to register for the Microsoft Hacktoberfest :)

[cezarsa]

So, the reasoning for Go Structs to use the Class icon was because Go structs might look a bit more like classes in other languages since they can have methods. Also, C++ structs use the Class icon as well.

Using Struct icons for other types was arbitrary really, I didn't know exactly what icon to use on them. After taking a look at how the C extension handles this I found out that it uses the Enum icon for typedef declarations. Maybe I should also switch other types to the Enum icon for consistency?

[ramya-rao-a]

Ah, ok. That makes sense.
I dont have a preference for Enum icon over Struct icon, so let's go with what you have at the moment.
If we get any feedback around this, then we can act on it.