Overhaul the navigation menu to add configuration options

[caendesilva]

Abstract

In the spirit of convention over configuration, most features added here don't majorly impact the default behavior of the app (with the exception of automatically hiding 404 pages). However, it brings several configuration options such as custom navigation menu links (thus removing the need of redirect hacks), as well as a blacklist (which is what hides the 404 by default).

Fixes

This PR fixes the following,

• Resolves Feature: Add custom links to the navigation menu in the config #16
• Resolves Feature: Automatically add a navigation menu link to the docs #25
• Resolves Feature: Add config option to hide pages from the navbar (default: '404') #26

Features

Custom navigation links

The custom navigation links can also be used to override and reorder the automatic links.

The links are added in the config/hyde.php file, and the syntax for adding custom links is documented in the config.

// External link
[
    'title' => 'GitHub',
    'destination' => 'https://github.com/hydephp/hyde',
    'priority' => 1200,
],

// Internal link (Hyde automatically resolves relative paths)
[
    'title' => 'Featured Blog Post',
    'slug' => 'posts/hello-world',
    // The 'priority' is not required.
]

Changes

The deprecated MakeNavigationLinkCommand has been removed as it is no longer needed.