Just a Javascript template with basic functions to open and save files locally on PC; no online hosting needed.
Modern javascript allows easily accessing local files both for reading and writing; for security reasons this canNOT be don automatically, but it's just a matter of asking to the user to select the file to be opened or to specify where to save a file.
This repo just contains a basic source code for opening a file and saving memory contents to a file. It's not a library; just copy&paste the source, then start writing your amazing new program. ;-)