Minor fixes since refactor to expo framework

• Fix podcasts screen
• Fix video screen
• Extract ArticleItem component in order to reuse it in Podcast and Video screens
• Fix Keep Screen On feature
• Align codebase to expo by removing @react-navigation/native

Refactor to expo framework

App was refactored to expo framework

Included

• articles are now working again, with embedded webview to preload the article (#86)
• add a carousel to browse a special category of articles

Minor adjustements in header and article

Patch release since 3.3.0

• Fetch best image when possible when reading an article
• Make header fixed and smaller when browsing a video