Plato 0.7.7

• Implement text selection.
• Implement highlights and annotations.
• Allow searching for more than one word.
• Allow starting a search without bringing up the bottom bar.
• Introduce swipe sequences (cf. doc/MANUAL.md).
• Recompute the top offset when cropping margins.
• Article fetcher: decode character entities in titles.
• Fix two bugs that would trigger an infinite loop when searching text:
  • In a static document that contains pages without text.
  • If the value of current_page is invalid.