Restore AppVeyor CI for Windows tests

.appveyor.yml

@@ -0,0 +1,34 @@
+image: Visual Studio 2019
+
+environment:
+  global:
+    RANDOM_SEED: 0
+  matrix:
+    - PYTHON_MAJOR: 3
+      PYTHON_MINOR: 8
+
+cache:
+  - .venv -> poetry.lock
+
+init:
+  - git config --global core.symlinks true
+
+install:
+  # Add Make and Python to the PATH
+  - copy C:\MinGW\bin\mingw32-make.exe C:\MinGW\bin\make.exe
+  - set PATH=%PATH%;C:\MinGW\bin
+  - set PATH=C:\Python%PYTHON_MAJOR%%PYTHON_MINOR%;%PATH%
+  - set PATH=C:\Python%PYTHON_MAJOR%%PYTHON_MINOR%\Scripts;%PATH%
+  # Install system dependencies
+  - curl -sSL https://install.python-poetry.org | python -
+  - set PATH=%USERPROFILE%\AppData\Roaming\Python\Scripts;%PATH%
+  - make doctor
+  # Install project dependencies
+  - make install
+
+build: off
+
+test_script:
+  - make check
+  - make test
+  - make demo

README.md

@@ -4,7 +4,8 @@ Gitman is a language-agnostic dependency manager using Git. It aims to serve as
 
 [![Demo](https://raw.githubusercontent.com/jacebrowning/gitman/main/docs/demo.gif)](https://asciinema.org/a/3DLos4HIU84P0AfFlZMYcgPus)
 
-[![Build Status](https://img.shields.io/github/actions/workflow/status/jacebrowning/gitman/main.yml?branch=main)](https://github.com/jacebrowning/gitman/actions)
+[![Unix Build Status](https://img.shields.io/github/actions/workflow/status/jacebrowning/gitman/main.yml?branch=main&label=unix)](https://github.com/jacebrowning/gitman/actions)
+[![Windows Build Status](https://img.shields.io/appveyor/ci/jacebrowning/gitman/main.svg?label=window)](https://ci.appveyor.com/project/jacebrowning/gitman)
 [![Code Coverage](https://img.shields.io/codecov/c/gh/jacebrowning/gitman)](https://codecov.io/gh/jacebrowning/gitman)
 [![Code Quality](https://img.shields.io/scrutinizer/g/jacebrowning/gitman.svg?label=quiality)](https://scrutinizer-ci.com/g/jacebrowning/gitman/?branch=main)
 [![PyPI License](https://img.shields.io/pypi/l/gitman.svg)](https://pypi.org/project/gitman)