title: Remove TypeScript type annotations and assertions from code base
body: <p>Considering that there is a project that should be converted from TypeScript to Babel, files contain typing information that cannot be just ignored by Babel.</p>
  
  <p>How can TS type annotations and assertions be stripped off from the entire code base in automatic manner?</p>
  
  <p>Is there a way to convert them to Flow (considering that some TS type features can be converted and some can't)?</p>
  
  <p>Obviously, this cannot be obtained via regexps.</p>
  
  <p><em>The project has a lot of TS/ES.next features in its code and supposed to be readable and editable, transpiling with <code>es6</code> target is not an option here.</em></p>