feat: Add obisidian API's free functions to API

[dljsjr]

Adds the Obsidian free functions to the app object under the functions object.

This provides access to a bunch of useful built-in Obsidian utilities via the local API.

[blacksmithgu]

Aren't these already available as app.<function>? I thought the Obsidian app object was already in the global context.

[FeralFlora]

Aren't these already available as app.<function>? I thought the Obsidian app object was already in the global context.

Usage of global app is discouraged, see:
https://docs.obsidian.md/Plugins/Releasing/Plugin+guidelines#Avoid+using+global+app+instance

and:
https://github.com/Fevol/obsidian-typings/blob/main/CHANGELOG.md#114

NOTE: the global app variable has been removed from the official Obsidian API as of 1.6.0, it will not be re-added by obsidian-typings

[dljsjr]

Aren't these already available as app.<function>? I thought the Obsidian app object was already in the global context.

No, the free functions like normalizePath aren't attached to the app object. They're exported as part of the obsidian namespace, meaning they aren't available to code blocks since you can't import "obsidian"