`Scratch` -- a "scratchpad" for your node- or page-scoped variables. In most cases you can do well without `Scratch`, but there are some use cases that aren't solvable with Go's templates without `Scratch`'s help, due to scoping issues.
`Scratch` is added to both `Node` and `Page` and `Shortcode` -- with following methods:
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* `Set` and `Add` takes a `key` and the `value` to add.
* `Get` returns the `value` for the `key` given.
* `SetInMap` takes a `key`, `mapKey` and `value`