Added main UI file.

sohstationviewer/view/main_ui.py

+import os.path
+
+from PySide2.QtUiTools import QUiLoader
+from PySide2.QtCore import QFile, QIODevice
+
+
+def load_main_ui(base_path=''):
+    file_name = os.path.join(base_path, 'main.ui')
+    ui_file = QFile(file_name)
+
+    if not ui_file.open(QFile.ReadOnly):
+        print(f'cannot open {file_name}', ui_file.errorString())
+
+    loader = QUiLoader()
+    window = loader.load(ui_file)
+
+    ui_file.close()
+
+    if not window:
+        print(loader.errorString())
+
+    return window
+