Python bindings configured correctly for PyPI releases (#54)

* Python bindings sep 2023 (#52)

* Added maturin-based Python binding, to be deployed to https://pypi.org/project/vtracer/

* Removed poetry mentions from pyproject.toml, added README_PY.md for use on PYPI

* ->   v0.6.1
-> moved Python bindings to bottom of converter.rs

* - README_PY.md needed to be inside the cmdapp directory to display on PyPi.irg
->  v0.6.3

* Move code around

* Edit Readme

* Edit RELEASES.md

* Feature guard

* Build wheels with the cmdapp/Cargo.toml rather than top-level Cargo.toml

* use cmdapp/Cargo.toml for all Maturin CI actions, which causes Github to build all platforms python wheels and submit a new release to PyPI

* Bump to 0.6.4 for new PyPI release with all platforms' wheels included

* PyPI didn't accept a 'linux_aarch64' wheel for a release. For the moment, remove the platform until I can convince the action to build 'manylinux_aarch64' or the like

* Version bump while I work out CI & PyPI release wrinkles

* Maturin authors say `compatibility = "linux"` in pyproject.toml is causing PyPI failure. Replacing with "manylinux2014"

* bump to v0.7.0 in preparation for release from original vtracer repo

---------

Co-authored-by: Chris Tsang <chris.2y3@outlook.com>

cmdapp/Cargo.toml

@@ -1,8 +1,8 @@
 [package]
 name = "vtracer"
-version = "0.5.0"
-authors = ["Chris Tsang <tyt2y7@gmail.com>"]
-edition = "2018"
+version = "0.7.0"
+authors = ["Chris Tsang <chris.2y3@outlook.com>"]
+edition = "2021"
 description = "A cmd app to convert images into vector graphics."
 license = "MIT OR Apache-2.0"
 homepage = "http://www.visioncortex.org/vtracer"
@@ -14,4 +14,8 @@ keywords = ["svg", "computer-graphics"]
 clap = "2.33.3"
 image = "0.23.10"
 visioncortex = { version = "0.8.0" }
-fastrand = "1.8"
+fastrand = "1.8"
+pyo3 = { version = "0.19.0", optional = true }
+
+[features]
+python-binding = ["pyo3"]