Enso will now associate with two file extensions:
* `.enso` — Enso source file.
* If the source file belongs to a project under the Project Manager-managed directory, it will be opened.
* If the source file belongs to a project located elsewhere, it will be imported into the PM-managed directory and opened;
* Otherwise, opening the `.enseo` file will fail. (e.g., loose source file without any project)
* `.enso-project` — Enso project bundle, i.e., `tar.gz` archive containing a compressed Enso project directory.
* it will be imported under the PM-managed directory; a unique directory name shall be generated if needed.
### Important Notes
On Windows, the NSIS installer is expected to handle the file associations.
On macOS, the file associations are expected to be set up after the first time Enso is started,
On Linux, the file associations are not supported yet.
