feat: Windows support using MinGW-w64 (#4201)

Building tree-sitter on Windows within a Cygwin or MSYS2 environment
for MinGW-w64 targets should work. As there's no configure-like step,
the tools have to be specified with:

    make CC=x86_64-w64-mingw32-gcc \
         AR=x86_64-w64-mingw32-ar \
         STRIP=x86_64-w64-mingw32-strip

Useful reference:
[How to build and use DLLs on Windows](https://nullprogram.com/blog/2021/05/31/)

This commit doesn't tag public functions with dllexport or
dllimport. This results in exporting non-static functions visible
between translation units, and generating slightly less efficient code
for calling exported functions from the DLL.

This commit doesn't include support to build libtree-sitter with MSVC or
clang-cl, but generates a libtree-sitter.lib file for MSVC/clang-cl
consumers.

.github/workflows/build.yml

@@ -163,6 +163,14 @@ jobs:
       env:
         CFLAGS: -g -Werror -Wall -Wextra -Wshadow -Wpedantic -Werror=incompatible-pointer-types
 
+    - name: Build C library on Windows (make)
+      if: ${{ runner.os == 'Windows' }}
+      run: make.sh -j CC="$CC" CFLAGS="$CFLAGS" AR="$AR"
+      env:
+        CC: x86_64-w64-mingw32-gcc
+        AR: x86_64-w64-mingw32-ar
+        CFLAGS: -g -Werror -Wall -Wextra -Wshadow -Wpedantic -Werror=incompatible-pointer-types
+
     - name: Build C library (CMake)
       if: ${{ !matrix.use-cross }}
       run: |