Added TypeScript for frontend

Added type definitions for components, functions, data
Added guards for network responses
fixes #8

front/src/App.css

@@ -1,16 +1,16 @@
 body {
-    height: 100vh;
-    overflow: hidden;
-    color: white;
-    font-family: sans-serif;
+  height: 100vh;
+  overflow: hidden;
+  color: white;
+  font-family: sans-serif;
 }
 
 .modal-content, .modal-content .form-select {
-    background-color: rgb(17, 17, 17) !important;
+  background-color: rgb(17, 17, 17) !important;
 }
 
 /* В связи со сложившейся политической обстановкой */
 .leaflet-attribution-flag {
-    position: absolute;
-    right: -100px;
+  position: absolute;
+  right: -100px;
 }