Changes shebang of executables to `/usr/bin/env` (#388)

# Description

This MR replaces `#!/bin/bash` with `#!/usr/bin/env bash`. This fetches
the executable from the `PATH` instead of having the path fixed. This
makes it more robust on different Unix systems. It should also allow you
to use bash scripts with zshell as well.

Fixes #384

## Type of change

- Bug fix (non-breaking change which fixes an issue)

## Checklist

- [x] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./orbit.sh --format`
- [ ] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] I have run all the tests with `./orbit.sh --test` and they pass
- [ ] I have updated the changelog and the corresponding version in the
extension's `config/extension.toml` file
- [x] I have added my name to the `CONTRIBUTORS.md` or my name already
exists there

docker/cluster/submit_job.sh

-#!/bin/bash
+#!/usr/bin/env bash
 
 # in the case you need to load specific modules on the cluster, add them here
 # e.g., `module load eth_proxy`

docker/container.sh

-#!/bin/bash
+#!/usr/bin/env bash
 
 #==
 # Configurations

orbit.sh

-#!/bin/bash
+#!/usr/bin/env bash
 
 # Copyright (c) 2022-2024, The ORBIT Project Developers.
 # All rights reserved.
@@ -127,7 +127,7 @@ setup_conda_env() {
     mkdir -p ${CONDA_PREFIX}/etc/conda/deactivate.d
     # add variables to environment during activation
     local isaacsim_setup_conda_env_script=${ORBIT_PATH}/_isaac_sim/setup_conda_env.sh
-    printf '%s\n' '#!/bin/bash' '' \
+    printf '%s\n' '#!/usr/bin/env bash' '' \
         '# for isaac-sim' \
         'source '${isaacsim_setup_conda_env_script}'' \
         '' \
@@ -141,7 +141,7 @@ setup_conda_env() {
     # needed because deactivate complains about orbit alias since it otherwise doesn't exist
     conda activate ${env_name}
     # remove variables from environment during deactivation
-    printf '%s\n' '#!/bin/bash' '' \
+    printf '%s\n' '#!/usr/bin/env bash' '' \
         '# for orbit' \
         'unalias orbit &>/dev/null' \
         '' \

source/standalone/tools/blender_obj.py

-#!/usr/bin/python
+#!/usr/bin/env python
 
 # Copyright (c) 2022-2024, The ORBIT Project Developers.
 # All rights reserved.

source/standalone/tools/process_meshes_to_obj.py

-#!/usr/bin/python
+#!/usr/bin/env python
 
 # Copyright (c) 2022-2024, The ORBIT Project Developers.
 # All rights reserved.