Show table of contents by default on wide screens

Summary:
Show table of content in left whitespace area in wide screens (width >= 1792px)

Closes T15920

Test Plan:

1. Open Phriction wiki page in browser which contain a number of chapter titles
2. Open Responsive Design Mode in browser (Ctrl-Shift-M in Firefox) and test different width's of the page (e.g. 1024, 1280, 1440, 1600, 1920, ...)
3. Open Remarkup Reference at /book/phorge/article/remarkup/ and repeat step 2
4. Open a Differential revision to confirm that the unrelated ToC panel has no changes

Reviewers: O1 Blessed Committers, aklapper

Reviewed By: O1 Blessed Committers, aklapper

Subscribers: aklapper, tobiaswiese, valerio.bozzolan, Matthew, Cigaryno

Maniphest Tasks: T15920

Differential Revision: https://we.phorge.it/D25790