Developer documentation updates

Summary

Couple of updates of developer documentation How To Guides in response to volunteer work + small cleanup.

Adds Preview Kolibri on a mobile device, a new guide for previewing Kolibri in web app mode on simulated and real mobile devices
In Running Kolibri with local Kolibri Design System, highlights the warning about relative vs absolute KDS path by formatting it as such
In the Getting started -> Sample resource and data, adds a link to reference the Kolibri user guide on importing with token.
Makes heading levels across all How To guides consistent

Reviewer guidance

Preview the links above
Confirm that both options to run Kolibri on a real mobile device work as expected when following step by step

Comments

@nucleogenesis @rtibbles I am not entirely sure how pre-existing https://kolibri-dev.readthedocs.io/en/develop/manual_testing/app_plugin/index.html fits into the mobile device landscape. Does this command simulate Android? If so, should we cross-reference with the new mobile device guide, or place these two pages close to each other, or even have on a single page? And how should I best explain in what cases app plugin is preferred?

Asset type	Download link
PEX file	kolibri-0.18.0.dev0_git.20241115202159.pex
Windows Installer (EXE)	kolibri-0.18.0.dev0+git.20241115202159-windows-setup-unsigned.exe
Debian Package	kolibri_0.18.0.dev0+git.20241115202159-0ubuntu1_all.deb
Mac Installer (DMG)	kolibri-0.18.0.dev0+git.20241115202159.dmg
Android Package (APK)	kolibri-0.18.0.dev0+git.20241115202159-0.1.4-debug.apk
TAR file	kolibri-0.18.0.dev0+git.20241115202159.tar.gz
WHL file	kolibri-0.18.0.dev0+git.20241115202159-py2.py3-none-any.whl

learningequality / kolibri