Switch heredoc & BASH_SOURCE to POSIX compliant

Switch heredoc & BASH_SOURCE to POSIX compliant

commit f2b591e93af3d3a210c5f8305643271fde4235eb
Author: b3nj4m1n <b3nj4m1n@gmx.net>
Date:   Sat May 14 17:21:03 2022 +0200

    Heredoc & BASH_SOURCE

commit b52561fa1db78cdf9a82da829c3ba32c1d30455e
Author: b3nj4m1n <b3nj4m1n@gmx.net>
Date:   Sat May 14 17:16:05 2022 +0200

    Revert "POSIX compliancy"

    This reverts commit 4cad6152d25430956c48a9fe606323b8a22a0600.

commit 4cad6152d25430956c48a9fe606323b8a22a0600
Author: 2641a40fd44383320adde4b027a1d0b03bd550 <58827198+2641a40fd44383320adde4b027a1d0b03bd550@users.noreply.github.com>
Date:   Sat May 14 11:08:21 2022 +0500

    POSIX compliancy