[Maintenance] Replace all the any with TS types

[epatrasc]

Is your feature request related to a problem? Please describe.

We have lots of "any" as type, we should fix this.

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Add the correct type for all the any

[edmorrish]

Have started a branch with tsc in strict mode to try to resolve some of this: https://github.com/bbc/lrud/tree/strict-types

[edmorrish]

Types are extremely messy across the board to be honest, almost everything is nullable or undefined at all times so it'd probably be a good idea to do a review of the Lrud data structure and come up with some sensible defaults for the constructor.