[gnome-themes-extra: 1/4] Update the README and port it to Markdown

[Juraj Fiala <jurf src gnome org>]

commit fa9777309c6910e5ffc9991a8f884f201273baf6
Author: Juraj Fiala <jurf riseup net>
Date:   Wed Jan 24 18:10:33 2018 +0100

    Update the README and port it to Markdown

 README    | 18 ------------------
 README.md | 28 ++++++++++++++++++++++++++++
 2 files changed, 28 insertions(+), 18 deletions(-)
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diff --git a/README.md b/README.md
new file mode 100644
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+gnome-themes-extra
+==================
+
+This module houses themes and theme-y tidbits that don’t really fit in anywhere
+else, or deserve their own module. At the moment this consists of:
+
+ * the GTK+ 2 version of Adwaita
+ * Adwaita-dark as a separate theme, along with its GTK+ 2 equivalent
+ * GTK+ 2 versions of the HighContrast themes
+ * index files needed for Adwaita to be used outside of GNOME
+
+Once named `gnome-themes-standard`, this module used to contain various
+components of the default GNOME 3 theme. However, at this point, most it has
+moved elsewhere. The GTK+ 3 versions of the Adwaita and HighContrast themes are
+now part of GTK+ 3 itself, and the HighContrastInverse and LowConstrast themes
+have been discontinued.
+
+Not to be confused with `gnome-themes-extras`.
+
+How to report bugs
+------------------
+
+You can report issues you find on GNOME’s [GitLab][1], or chat about them on
+[IRC][2], in [#gnome-design][3].
+
+[1]: https://gitlab.gnome.org/GNOME/gnome-themes-extra/issues
+[2]: https://wiki.gnome.org/Community/GettingInTouch/IRC
+[3]: irc://irc.gnome.org/gnome-design