dev-python/toposort: new pakage, move from Science and Guru overlays

Since this package is common dependecy for packages
from both overlays it's offered to bring it to portage tree.

Packages that depend on dev-python/toposort:

in Science overlay
    dev-python/cadquery-pywrap
    dev-python/snakemake
        (PYTHON_TARGETS is required to be upd. to 8..9 or 8..10)

in GURU overlay
    app-doc/ford

Ebuild is picked up from Science overlay with the following chages:
    - PYTHON_TARGETS updated to 8..10 (instead of 7..9);
    - Add proxied-maintainer via Gentoo Scince Project.

After addition package to portage tree
it could be removed from mentioned above overalays.

Signed-off-by: Sergey Torokhov <torokhov-s-a@yandex.ru>
Closes: https://github.com/gentoo/gentoo/pull/22330
Signed-off-by: Andrew Ammerlaan <andrewammerlaan@gentoo.org>

dev-python/toposort/Manifest

@@ -0,0 +1 @@
+DIST toposort-1.6.tar.gz 11690 BLAKE2B a9a57fd182a3324d43112c3f84a20039f032d99bf2c35c6678a6a08c23b123f18610f460529dd39c769b935d98270a25ded2f1a483e4e6f06d3ccc501b340cb8 SHA512 8dc30b5d5a6f476756520236bc93840243690779783ec8f0b5ef0f72c64d774177b25d10d2e024cda968f81352abbc4f89f3069760fc3a86bd5ee387e7951928

dev-python/toposort/metadata.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd">
+<pkgmetadata>
+	<maintainer type="person" proxied="yes">
+		<email>torokhov-s-a@yandex.ru</email>
+		<name>Sergey Torokhov</name>
+	</maintainer>
+	<maintainer type="project" proxied="proxy">
+		<email>sci@gentoo.org</email>
+		<name>Gentoo Science Project</name>
+	</maintainer>
+	<stabilize-allarches/>
+	<upstream>
+		<remote-id type="gitlab">ericvsmith/toposort</remote-id>
+		<remote-id type="pypi">toposort</remote-id>
+	</upstream>
+</pkgmetadata>

dev-python/toposort/toposort-1.6.ebuild

@@ -0,0 +1,18 @@
+# Copyright 1999-2021 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+PYTHON_COMPAT=( python3_{8..10} )
+
+inherit distutils-r1
+
+DESCRIPTION="Implements a topological sort algorithm"
+HOMEPAGE="https://gitlab.com/ericvsmith/toposort"
+SRC_URI="mirror://pypi/${PN:0:1}/${PN}/${P}.tar.gz"
+
+LICENSE="Apache-2.0"
+SLOT="0"
+KEYWORDS="~amd64 ~x86"
+
+distutils_enable_tests setup.py