remove build command, add dev command, remove outdated package @types…

[tsvetkovv]

• removed outdated @types/date-fns

  This is a stub types definition for date-fns (https://github.com/date-fns/date-fns). date-fns provides its own type definitions, so you don't need @types/date-fns installed!

• moved index.ts under src folder in order to keep all source files under one roof
• build command was replaced to check-types to avoid confusions.
• added dev command with nodemon for auto-reloading running scripts. Although, we may not want that because accidental reload would cause the app state loss since the app state stored in memory exclusively. What do you think?

[A77AY]

я бы состояние вынес в файл или sqlite например (в будущем, только 2 сек слишком частое, надо будет реже)

[A77AY]

nodemon норм