Allow altering of other file types

[mgrsskls]

It would be nice to have the possibility to alter other file types (similar to alter_json_file and alter_yaml_file).

My current use case is that I simply want to append something to an existing file (i.a. adding more lines to a .gitignore). In that case something something like append_to_file(".gitignore", "node_modules") would be cool!

[stmh]

In the meantime you can use bash for that, e.g.

- echo "ignore_me" >> %rootFolder%/.gitignore