Fix reference to deprecated handlebars type

[adidahiya]

from handlebars.d.ts:

// NOTE: for backward compatibility of this typing
type HandlebarsTemplateDelegate<T = any> = Handlebars.TemplateDelegate<T>;

turns out it's not actually backwards compatible because they haven't declared it as an ambient global type of subtle differences in type acquisition (see below). but anyway, typedoc should use the new namespaced type. I've gone ahead and done that in this PR.

unblocks palantir/documentalist#86
cc @styu

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edit: more info

Another way to solve this would be with an import "handlebars"; statement in any typedoc module which references a global handlebars symbol like HandlebarsTemplateDelegate. But adding import statements just for type acquisition side effects is bad.

When handlebars switched to publishing its own types, they did a straight port of @types/handlebars. However, the semantics for acquiring types from node_modules/@types/handlebars is a little different from node_modules/handlebars. TypeScript will automatically pull in all ambient types from node_modules/@types and make symbols like HandlebarsTemplateDelegate available, but the same is not true for types bundled in a regular npm package.

Related to this (but external to this repo), there's no need for declare module statements in handlebars' types anymore. The type system will acquire types from the same location as the module system, so declare module "handlebars" is unnecessary.

[aciccarello]

Great! Thanks for the PR!

[raymondfeng]

@aciccarello Would you please publish a new release to npm?