[gtksourceview] Add the GtkSourceView logo to git

[Sébastien Wilmet <swilmet src gnome org>]

commit 29f52773dd065aaec95d34c6b60c90ab20cba855
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Sun Jun 17 11:20:58 2018 +0200

    Add the GtkSourceView logo to git
    
    It's not me who created it. It was on the GtkSourceView website and then
    on the wiki. But on the wiki someone can delete the attachment, so it's
    safer to have a copy in git.

 data/GtkSourceView-logo.png | Bin 0 -> 21775 bytes
 1 file changed, 0 insertions(+), 0 deletions(-)
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diff --git a/data/GtkSourceView-logo.png b/data/GtkSourceView-logo.png
new file mode 100644
index 00000000..03a2921c
Binary files /dev/null and b/data/GtkSourceView-logo.png differ