Improve bump-my-version usage (#296)

.bumpversion.toml

@@ -0,0 +1,17 @@
+[tool.bumpversion]
+current_version = "0.9.6"
+tag = true
+commit = true
+parse = "(?P<major>\\d+)\\.(?P<minor>\\d+)\\.(?P<patch>\\d+)"
+serialize = ["{major}.{minor}.{patch}"]
+search = "{current_version}"
+replace = "{new_version}"
+tag_name = "v{new_version}"
+tag_message = "Bump version: {current_version} → {new_version}"
+message = "Bump version: {current_version} → {new_version}"
+
+[[tool.bumpversion.files]]
+filename = "pyproject.toml"
+
+[[tool.bumpversion.files]]
+filename = "src/nexgen/__init__.py"