Added support for root typealiases

[666tos]

Mock template was customised to add single feature, which I named root-typealiases

Root typealiases are placed in root of the resulting file and are NOT nested inside type (as typealiases do). They are meant to solve problem partially described in https://github.com/MakeAWishFoundation/SwiftyMocky/issues/184 Problem occurs when mock is generated for protocol name, which clashes with type from another library. Since there is no concept of module in Sourcery/SwiftyMocky, compiler gets confused which type should be used for inheritance, for example:

Typealias example:

Our module:

    //sourcery: root-typealias = "Feature = MyModule.Feature"
    protocol Feature: AutoMockable {}

Another module:

    public struct Feature {}

Resulting Mock.generated.swift:

    open class FeatureMock: Feature, Mock { <--- 'Feature' is ambiguous for type lookup in this context
        public typealias Feature = MyModule.Feature
    } 

In this implementation this problem can be fixed by adding annotation for Feature protocol, like this:

    //sourcery: root-typealias = "Feature = MyModule.Feature"
    protocol Feature: AutoMockable {}

Resulting Mock.generated.swift:

    public typealias Feature = MyModule.Feature
    open class FeatureMock: Feature, Mock {}  <--- No ambiguity for type lookup in this context