Preliminary, but added minimalistic typing check to tox and CI, as well as a py.typed file.

- The py.typed file is very early, but it's necessary to verify type completeness via `pyright --verifytypes`. Seems like the right kind of typing check, but that's assuming pyright and not mypy is ultimately used.
 - Reference: https://microsoft.github.io/pyright/#/typed-libraries?id=verifying-type-completeness
- Add typing testenv to tox.ini, which will run `pyright --verifytypes rfc3986`.
- Add one more matrix slot to the GitHub workflow to run the above typing check in CI on the lowest supported version of python on Ubuntu.
 - I only added it for Ubuntu because this package and its dependencies are pure python, so the types shouldn't change between operating systems.

Author: Sachaa-Thanasius

.github/workflows/main.yml

@@ -19,6 +19,10 @@ jobs:
         - os: windows-latest
           python: '3.12'
           toxenv: py
+        # typing
+        - os: ubuntu-latest
+          python: '3.8'
+          toxenv: typing
         # misc
         - os: ubuntu-latest
           python: '3.12'

src/rfc3986/py.typed

@@ -1,5 +1,5 @@
 [tox]
-envlist = py{37,38,39,310,311,312},lint
+envlist = py{37,38,39,310,311,312},lint,typing
 
 [testenv]
 pip_pre = False
@@ -39,6 +39,11 @@ deps =
     flake8-import-order
 commands = flake8 {posargs} src/rfc3986
 
+[testenv:typing]
+deps =
+    pyright
+commands = pyright {posargs:--verifytypes rfc3986}
+
 [testenv:venv]
 commands = {posargs}