Accept files with extension XML as well (#216)

When exporting data from the Solinst Levelogger Software, the extension '.xml' is used. Files with this extension can be read as well.

Co-authored-by: OnnoEbbens <onnoebbens@gmail.com>

hydropandas/io/solinst.py

@@ -33,7 +33,7 @@ def read_solinst_file(
     # open file
     path = str(path)
     name = os.path.splitext(os.path.basename(path))[0]
-    if path.endswith(".xle"):
+    if path.endswith(tuple([".xle", ".xml"])):
         f = path
     elif path.endswith(".zip"):
         zf = zipfile.ZipFile(path)