implement launch() function.

Allows launching nvda program at start.

src/nvda_voicemeeter/cdll.py

@@ -1,8 +1,41 @@
 import ctypes as ct
+import platform
+import winreg
 from pathlib import Path
 
+from .errors import NVDAVMError
+
 bits = 64 if ct.sizeof(ct.c_voidp) == 8 else 32
 
+if platform.system() != "Windows":
+    raise NVDAVMError("Only Windows OS supported")
+
+REG_KEY = "\\".join(
+    filter(
+        None,
+        (
+            "SOFTWARE",
+            "WOW6432Node" if bits == 64 else "",
+            "Microsoft",
+            "Windows",
+            "CurrentVersion",
+            "Uninstall",
+            "NVDA",
+        ),
+    )
+)
+
+
+def get_nvdapath():
+    with winreg.OpenKey(winreg.HKEY_LOCAL_MACHINE, r"{}".format(REG_KEY)) as nvda_key:
+        return winreg.QueryValueEx(nvda_key, r"UninstallDirectory")[0]
+
+
+try:
+    NVDA_PATH = Path(get_nvdapath()) / "nvda.exe"
+except FileNotFoundError as e:
+    NVDA_PATH = ""
+
 controller_path = Path(__file__).parents[2].resolve() / "controllerClient"
 if not controller_path.exists():
     controller_path = Path(__file__).parents[3].resolve() / "controllerClient"