write_manifest include extra files does not work when executed outside of target directory

[bcwu]

Related to #411

write_manifest include extras is bugged at the moment when we try to include the extra file from outside the folder:

mkdir app
touch app/.env app/main.py
pip install rsconnect-python==1.16.0
rsconnect write-manifest streamlit app app/.env

# Results:
> Checking arguments...                            [OK]
> Inspecting Python environment...                 [OK]
> Creating manifest.json...                        [ERROR]
Error: ../.env must be under app.

The temporary workaround by cd into the app directory before executing the command:

cd app
rsconnect write-manifest streamlit ./ ./env