Added Typescript support via JSDoc comments for some files.
The code has really outdated type signatures, so in order to fully type the codebase the changes need to be incremental.
To check the types run:
npx tsc
API changed walkFoo(ast, fun) to walk(ast,{visit: 'Rule',enter: fun)
csstree.translate renamed to csstree.generate
csstree.generate throws an error on invalid style where translate silently ignored it - update style processing to catch and ignore instead
Updated tests - csstree now omits more whitespace
