allow skare3_tools config in the HOME directory (#110)

add the skare3_tools config in the HOME directory if the other options are not available

skare3_tools/config.py

@@ -12,6 +12,10 @@
 
 - specified by the SKARE3_TOOLS_DATA environmental variable,
 - or in the directory $SKA/data/skare3/skare3_data
+- or:
+
+  - Linux/Mac OS: ~/.skare3
+  - windows: %LOCALAPPDATA%\\skare3
 
 The default looks like this:
 
@@ -103,11 +107,25 @@
 
 
 def _app_data_dir_():
-    ska_data_dir = os.path.join(os.environ["SKA"], "data", "skare3", "skare3_data")
+    home_dir = os.path.expanduser("~")
     if "SKARE3_TOOLS_DATA" in os.environ:
         app_data_dir = os.environ["SKARE3_TOOLS_DATA"]
-    elif os.path.exists(ska_data_dir):
+    elif (
+        "SKA" in os.environ
+        and (
+            ska_data_dir := os.path.join(
+                os.environ["SKA"], "data", "skare3", "skare3_data"
+            )
+        )
+        and os.path.exists(ska_data_dir)
+    ):
         app_data_dir = ska_data_dir
+    elif local_app_data_dir := os.getenv("LOCALAPPDATA"):
+        # this is the windows location
+        app_data_dir = os.path.join(local_app_data_dir, "skare3")
+    elif os.path.exists(home_dir) and os.access(home_dir, os.W_OK):
+        # can use this in linux and Mac OS
+        app_data_dir = os.path.join(home_dir, ".skare3")
     else:
         app_data_dir = None
     return app_data_dir