firebase.admin() does not seem to offer create, read, update, and delete (CRUD) operations on Firebase Hosting.
What would be the recommended way to write a file to Firebase Hosting programmatically?
While there is no official SDK (as Doug says, the official API is REST-based), you can import firebase-tools
into a Node.js script and use it like an API.
While neither of these officially allow you to deploy a single file, you can use it creatively to get what you want. See my Gist here: https://gist.github.com/puf/e00c34dd82b35c56e91adbc3a9b1c412, which gives you an command line tool like this:
node deployFile.js <site_name> <file_to_deploy> [commit]