Add a new image in the markdown help page

Previously we were linking directly from the public/
directory. While this worked for the GitLab help page,
it was not working for doc.gitlab.com. Adding an image
in a relative directory and linking from there serves
both ends.

[ci skip]

1 files changed, 0 insertions, 0 deletions

diff --git a/doc/markdown/img/logo.png b/doc/markdown/img/logo.png
new file mode 100644
index 00000000000..7da5f23ed9b
--- /dev/null
+++ b/doc/markdown/img/logo.png