Refactor simple-extension example to use poetry instead of tox

Author: kngwyu

examples/simple-extension/Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "numpy-example"
 version = "0.1.0"
-authors = ["Toshiki Teramura <[email protected]>"]
+authors = ["Toshiki Teramura <[email protected]>", "Yuji Kanagawa <[email protected]>"]
 edition = "2018"
 
 [lib]

examples/simple-extension/poetry.lock

@@ -0,0 +1,15 @@
+[build-system]
+build-backend = "maturin"
+
+[tool.poetry]
+name = "numpy-example"
+version = "0.1.0"
+description = "A minimum example of rust-numpy"
+authors = ["Toshiki Teramura <[email protected]>", "Yuji Kanagawa <[email protected]>"]
+
+[tool.poetry.dependencies]
+numpy = ">=1.18"
+python = ">=3.6"
+
+[tool.poetry.dev-dependencies]
+pytest = "^6.1"