[gimp] devel-docs: move HACKING from root EXTRA_DIR to devel-docs one.

[Jehan <jehanp src gnome org>]

commit 8a3ff1a7b683debfe38a568eaf3ad54c6b42091f
Author: Jehan <jehan girinstud io>
Date:   Tue Feb 8 18:59:48 2022 +0100

    devel-docs: move HACKING from root EXTRA_DIR to devel-docs one.
    
    Also adding the CODING_STYLE.md. There is actually the question whether
    we still want to track this docs files to package them in the tarballs.
    It made sense 20 years ago when devs were working from tarballs, but
    nowadays, devs are expected to work from git HEAD.
    
    Anyway this fixes the CI.

 Makefile.am            | 1 -
 devel-docs/Makefile.am | 2 ++
 2 files changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/Makefile.am b/Makefile.am
index cdc707f03d..687ce5ab3c 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -69,7 +69,6 @@ EXTRA_DIST = \
        ChangeLog.pre-2-4       \
        ChangeLog.pre-2-6       \
        ChangeLog.pre-git       \
-       HACKING                 \
        INSTALL                 \
        LICENSE                 \
        NEWS                    \
diff --git a/devel-docs/Makefile.am b/devel-docs/Makefile.am
index ca4a8cffe6..f291f6e1e8 100644
--- a/devel-docs/Makefile.am
+++ b/devel-docs/Makefile.am
@@ -7,6 +7,8 @@ SUBDIRS = \
        performance-logs
 
 EXTRA_DIST = \
+       CODING_STYLE.md                 \
+       HACKING.md                      \
        README.md                       \
        contexts.txt                    \
        debug-plug-ins.txt              \