doc: Update README to README.md for gitlab visibility

README

-Maps is a map application for GNOME.
-More information on https://wiki.gnome.org/Apps/Maps

README.md

+
+# GNOME Maps
+
+[![Pipeline status](https://gitlab.gnome.org/GNOME/gnome-maps/badges/master/build.svg)](https://gitlab.gnome.org/GNOME/gnome-maps/commits/master)
+[![Code coverage](https://gitlab.gnome.org/GNOME/gnome-maps/badges/master/coverage.svg)](https://gitlab.gnome.org/GNOME/gnome-maps/commits/master)
+
+This is [Maps](https://wiki.gnome.org/Apps/Maps), a map application for GNOME.
+
+## Hacking on Maps
+
+To build the development version of Maps and hack on the code
+see the [general guide](https://wiki.gnome.org/Newcomers/BuildProject)
+for building GNOME apps.
+
+### Build Dependencies
+
+Ubuntu: `sudo apt install libgjs-dev libgee-0.8-dev libfolks-dev libgeocode-glib-dev libchamplain-0.12-dev librest-dev`
+
+### Meson build
+
+* `mkdir _build`
+* `cd _build`
+* `meson ..`
+* `ninja`
+* `sudo ninja install`
+
+## How to report issues
+
+Report issues to the GNOME [issue tracking system](https://gitlab.gnome.org/GNOME/gnome-maps/issues).