Support Record as type alias

[Falx]

Although Record support has been added in #47 and type alias support is mentioned in #86, it seems that the combination of the two is still not working. The following statement:

export type ValuePreferences = Record<string, number>;

Produces an error when the ValuePreferences is used as a type in the code:

Could not load class or interface or other type Record from C:\Users\tdupont\Workspaces\CommunitySolidServer\dist\http\representation\RepresentationPreferences