[gspell] build: docs: add missing files to EXTRA_DIST

[Sébastien Wilmet <swilmet src gnome org>]

commit d376c60a8b86036adf6eebb15203f2e56758fc07
Author: Sébastien Wilmet <swilmet informatique-libre be>
Date:   Sat Apr 16 14:12:03 2022 +0200

    build: docs: add missing files to EXTRA_DIST
    
    Some of the content in these files were previously written on the wiki.
    But I prefer the main VCS of the project, and also to be able to write
    in Markdown or simple text files.

 docs/Makefile.am | 7 +++++++
 1 file changed, 7 insertions(+)
---
diff --git a/docs/Makefile.am b/docs/Makefile.am
index 034926c..b961747 100644
--- a/docs/Makefile.am
+++ b/docs/Makefile.am
@@ -1,3 +1,10 @@
 SUBDIRS = reference
 
+EXTRA_DIST = \
+       dev-notes.md \
+       faq.md \
+       flatpak-notes \
+       gspell.next.md \
+       more-information.md
+
 -include $(top_srcdir)/git.mk