Correct HooksObject typing due to normalization; add finally

[evankennedy]

Summary

• Tell us about the problem your pull request is solving.
  This pull request does 2 things:
  • allows for the generalized format of hook objects not requiring a HookMap (aka all, find, etc)
    The standardization of the object occurs here:
    

    feathers/packages/commons/src/hooks.ts

    Lines 69 to 85 in 656bae7

    	// Converts different hook registration formats into the
    	// same internal format
    	export function convertHookData (obj: any) {
    	let hook: any = {};
    	if (Array.isArray(obj)) {
    	hook = { all: obj };
    	} else if (typeof obj !== 'object') {
    	hook = { all: [ obj ] };
    	} else {
    	each(obj, function (value, key) {
    	hook[key] = !Array.isArray(value) ? [ value ] : value;
    	});
    	}
    	return hook;
    	}

  • adds the hook finally method to typings
    The code enabling this is in a few places throughout the file, but can be seen here:
    

    feathers/packages/feathers/lib/hooks/index.js

    Lines 156 to 159 in 3ad094e

    	before: getHooks(app, service, 'before', method),
    	after: getHooks(app, service, 'after', method, true),
    	error: getHooks(app, service, 'error', method, true),
    	finally: getHooks(app, service, 'finally', method, true)

• Are there any open issues that are related to this?
  No, I didn't see any
• Is this PR dependent on PRs in other repos?
  No

Other Information

I noticed finally is not listed in the docs: https://docs.feathersjs.com/api/hooks.html#registering-hooks
If it is not encouraged and will be removed in a future release, I suggest we add @deprecated, otherwise I believe it should be added as-is.

I added a PR for "DefinitelyTyped" here DefinitelyTyped/DefinitelyTyped#34897