Make keyboard shortcuts optional

In addition to the `{{docs-keyboard-shortcuts}}` component, there are some keyboard shortcuts baked into `controllers/application.js` and `docs-viewer/component.js` that are enabled on initialization. These can interfere with components that have custom keyboard interactions.

A configuration option that disables shortcut initialization could solve this issue for some users.

Start in controllers/application.js and docs-viewer/component.js, tracing the keyboard shortcuts enabled during initialization and how configuration is currently handled. Define the configuration entry point and verify that disabling it prevents those shortcuts while preserving the {{docs-keyboard-shortcuts}} component behavior.

Written by the indexing model from the issue text.