gnucash-on-flatpak master: Several improvements of README.md

[Frank H.Ellenberger]

Updated	 via  https://github.com/Gnucash/gnucash-on-flatpak/commit/6b3349d4 (commit)
	from  https://github.com/Gnucash/gnucash-on-flatpak/commit/50cbfffb (commit)



commit 6b3349d495ac8bde05fde5e361c74467d70bf233
Author: Frank H. Ellenberger <frank.h.ellenberger at gmail.com>
Date:   Tue Oct 22 07:10:41 2019 +0200

    Several improvements of README.md
    
    Add a few links,
    use syntaxhighlight,
    flatpak run --command=sh



Summary of changes:
 README.md | 47 +++++++++++++++++++++++++----------------------
 1 file changed, 25 insertions(+), 22 deletions(-)