Polish documentation catalogs

[defagos]

Description

This PR polishes documentation catalogs to have a more consistent documentation.

Changes made

• Use LLMs to rephrase content. This makes style and English more consistent. Additional proofreading was performed afterwards to ensure nothing is lost and that ideas conveyed are correct.
• Make some tutorials simpler (reduce number of steps, tighten code).
• Fix non-playing RTS VOD example.
• Fix incorrect links to SRG SSR internal wiki.
• Improve Player documentation sections (same as Apple documentation style).
• Make documentation clearer where appropriate.
• Replace generated header images with real ones.

Conventions

Here are some of the conventions applied. Those match the style of Apple documentation closely (e.g. SwiftUI documentation):

• Article titles start with gerund, sections start with verb.
• Articles titles use title case.
• Article section titles are only capitalized.
• Bullet points items with item name in bold / title case.
• "For example" uses US English style (e.g., a, b, c).
• Improve existing extensions. For some reason this also fixes documentation warnings appeared with Xcode 16.

Checklist

• APIs have been properly documented (if relevant).
• The documentation has been updated (if relevant).
• New unit tests have been written (if relevant).
• The demo has been updated (if relevant).