[calls] doc: Add manpage as reStructuredText

[Evangelos Ribeiro Tzaras <devrtz src gnome org>]

commit 0d6ceca32451d824e0c83da5afe21bfab628bc18
Author: Evangelos Ribeiro Tzaras <devrtz fortysixandtwo eu>
Date:   Tue May 31 20:02:05 2022 +0200

    doc: Add manpage as reStructuredText

 doc/gnome-calls.rst | 66 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)
---
diff --git a/doc/gnome-calls.rst b/doc/gnome-calls.rst
new file mode 100644
index 00000000..8f9f6f73
--- /dev/null
+++ b/doc/gnome-calls.rst
@@ -0,0 +1,66 @@
+.. _gnome-calls(1):
+
+===========
+gnome-calls
+===========
+
+----------------------
+Make and receive calls
+----------------------
+
+SYNOPSIS
+--------
+
+|   **gnome-calls** [OPTIONS...] [SIP/TEL URI]
+
+DESCRIPTION
+-----------
+
+``gnome-calls`` is a GTK based dialer for PSTN and SIP.
+
+It uses ModemManager to talk to the cellular modem for PSTN.
+Besides phone calls it also handles USSD.
+In the case of SIP it uses sofia-sip for the SIP signalling and GStreamer
+pipelines to deal with RTP payload of audio data.
+
+It works on desktops but also adjusts to small screen sizes like smart phones
+and other mobile devices.
+
+OPTIONS
+-------
+
+``-h, --help``
+
+  Show help options.
+
+``--help-all``
+
+  Show all help options.
+
+``--help-gapplication``
+
+  Show GApplication options.
+
+``--help-gtk``
+
+  Show GTK+ options.
+
+``--version``
+
+  Show program version.
+
+``--p, --provider=PLUGIN``
+
+  The plugins to use as call provider. Can be passed multiple times. Defaults to ModemManger and SIP (``-p 
mm -p sip``).
+
+``-l, --dial=NUMBER``
+
+  Dial a phone number (no need for the ``tel:`` URI scheme prefix).
+
+``-d, --daemon``
+
+  Whether to present the main window on startup.
+
+``-v, --verbose``
+
+  Enable verbose debug messages. Can be passed multiple times.