Use env to determine python3 location (#7447)

* Use env to determine python3 location

In general, it is recommended to use `#!/usr/bin/env python3` as the shebang instead of the hardcoded `!#/usr/bin/python3`.
See <https://stackoverflow.com/a/5709632> for more information.

* Use env to determine python3 location (macOS)

* List changes in Changelog

* Revert to /usr/bin/python3

Using `/usr/bin/env python3` instead of `/usr/bin/python3` would require the XCode command line developer tools.
This is not feasible.

CHANGELOG.md

@@ -28,6 +28,7 @@ Note that this project **does not** adhere to [Semantic Versioning](http://semve
 - We fixed an issue where groups generated from authors' last names did not include all entries of the authors' [#5833](https://github.com/JabRef/jabref/issues/5833)
 - The export to MS Office XML now uses the month name for the field `MonthAcessed` instead of the two digit number [#7354](https://github.com/JabRef/jabref/issues/7354)
 - We included some standalone dialogs from the options menu in the main preference dialog and fixed some visual issues in the preferences dialog. [#7384](https://github.com/JabRef/jabref/pull/7384)
+- We improved the linking of the `python3` interpreter via the shebang to dynamically use the systems default Python. Related to [JabRef-Browser-Extension #177](https://github.com/JabRef/JabRef-Browser-Extension/issues/177)
 
 ### Fixed
 

buildres/linux/jabrefHost.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python3
+#!/usr/bin/env python3
 
 import json
 import logging