Squash all "getting started" pages into a single one

[IlCallo]

Description
Clearly and concisely explain the problem.
You can mention unclear or missing information, typos, grammatical mistakes, etc.
Any contributions and suggestions are welcome!

Squash all "getting started" pages together, as they are all pretty short except UMD one.
This may have bad impact on SEO for these pages, but those pages are actually used just a couple times per developer, not really that problematic IMO

Website Section URL
Website live preview, paste the page URL or section name (eg. Docs, if it happens on all docs page) below.

https://quasar.beget.it/start/pick-quasar-flavour

[IlCallo]

Move "UMD/Standalone" option to be the last too

[IlCallo]

Remove https://quasar.beget.it/start/quasar-cli and directly link to https://quasar.beget.it/quasar-cli/installation
We probably need to integrate some of the docs from the first to the second one

Push more on Quasar CLI and suggest people to use it to start, instead of leaving the user to choose without a suggestion
Provide more info on why to use Quasar CLI and what to use in different contexts

[IlCallo]

Let's not squash all pages to just one, for now