Edit Reading Progress

[pnalvarez]

Currently we only create new readings with a predefined progress. This issue consists of giving the option to edit an existing reading from a book the user selected.

ACCEPTANCE CRITERIA*

AC1) When the user selects a book that has already a reading saved(in progress), the Book Details screen CTA title will be "Edit reading"
AC2) In the Start Reading screen, if reading already exists, navigation title should be "Edit Reading"
AC3) If book has already a registered reading, when confirming new progress, the progress is updated instead of creating a new reading.