build/pkgs/sage_docbuild/src: Update metadata

Author: Matthias Koeppe

build/pkgs/sage_docbuild/src/README.md

@@ -0,0 +1,23 @@
+================================================================================
+ Sage: Open Source Mathematics Software: Build system of the Sage documentation
+================================================================================
+
+About SageMath
+--------------
+
+   "Creating a Viable Open Source Alternative to
+    Magma, Maple, Mathematica, and MATLAB"
+
+   Copyright (C) 2005-2020 The Sage Development Team
+
+   https://www.sagemath.org
+
+SageMath fully supports all major Linux distributions, recent versions of macOS, and Windows (using Cygwin or Windows Subsystem for Linux).
+
+The traditional and recommended way to install SageMath is from source via Sage-the-distribution (https://www.sagemath.org/download-source.html).  Sage-the-distribution first builds a large number of open source packages from source (unless it finds suitable versions installed in the system) and then installs the Sage Library (sagelib, implemented in Python and Cython).
+
+
+About this pip-installable source distribution
+----------------------------------------------
+
+This is the build system of the Sage documentation, based on Sphinx.

build/pkgs/sage_docbuild/src/README.rst

@@ -2,8 +2,24 @@
 name = sage_docbuild
 version = file: VERSION.txt
 description = Sage: Open Source Mathematics Software: Build system of the Sage documentation
-long_description = file: README.md
+long_description = file: README.rst
+long_description_content_type = text/x-rst
 license = GNU General Public License (GPL) v2 or later
 author = The Sage Developers
-author_email = https://groups.google.com/group/sage-support
+author_email = sage-support@googlegroups.com
 url = https://www.sagemath.org
+
+classifiers =
+    Development Status :: 6 - Mature
+    Intended Audience :: Education
+    Intended Audience :: Science/Research
+    License :: OSI Approved :: GNU General Public License v2 or later (GPLv2+)
+    Operating System :: POSIX
+    Operating System :: MacOS :: MacOS X
+    Programming Language :: Python :: 3 :: Only
+    Programming Language :: Python :: 3.6
+    Programming Language :: Python :: 3.7
+    Programming Language :: Python :: 3.8
+    Programming Language :: Python :: 3.9
+    Programming Language :: Python :: Implementation :: CPython
+    Topic :: Scientific/Engineering :: Mathematics