added css for login page

app/public/css/login.css

@@ -0,0 +1,122 @@
+*{
+  margin: 0;
+  padding: 0;
+  box-sizing: border-box;
+  font-family: 'Open Sans', sans-serif;
+}
+
+html { 
+    background: url("../pictures/Gerätehaus.jpg") no-repeat center center fixed; 
+    -webkit-background-size: cover;
+    -moz-background-size: cover;
+    -o-background-size: cover;
+    background-size: cover;
+}
+
+body{
+  margin: 0;
+  padding: 0;
+  height: 100vh;
+  overflow: hidden;
+}
+.center{
+  position: absolute;
+  top: 40%;
+  left: 50%;
+  transform: translate(-50%, -50%);
+  width: 400px;
+  background: white;
+  border-radius: 10px;
+  box-shadow: 10px 10px 15px rgba(0,0,0,0.05);
+}
+.center h1{
+  text-align: center;
+  padding: 20px 0;
+  border-bottom: 1px solid silver;
+  font-weight: 400;
+  color: #002e5b;
+}
+.center form{
+  padding: 0 40px;
+  box-sizing: border-box;
+}
+form .txt_field{
+  position: relative;
+  border-bottom: 2px solid #adadad;
+  margin: 30px 0;
+}
+.txt_field input{
+  width: 100%;
+  padding: 0 5px;
+  height: 40px;
+  font-size: 16px;
+  border: none;
+  background: none;
+  outline: none;
+}
+.txt_field label{
+  position: absolute;
+  top: 50%;
+  left: 5px;
+  color: #adadad;
+  transform: translateY(-50%);
+  font-size: 16px;
+  pointer-events: none;
+  transition: .5s;
+}
+.txt_field span::before{
+  content: '';
+  position: absolute;
+  top: 40px;
+  left: 0;
+  width: 0%;
+  height: 2px;
+  background: #2691d9;
+  transition: .5s;
+}
+.txt_field input:focus ~ label,
+.txt_field input:valid ~ label{
+  top: -5px;
+  color: #2691d9;
+}
+.txt_field input:focus ~ span::before,
+.txt_field input:valid ~ span::before{
+  width: 100%;
+}
+.pass{
+  margin: -5px 0 20px 5px;
+  color: #a6a6a6;
+  cursor: pointer;
+}
+.pass:hover{
+  text-decoration: underline;
+}
+input[type="submit"]{
+  width: 100%;
+  height: 50px;
+  border: 1px solid;
+  background: #2691d9;
+  border-radius: 25px;
+  font-size: 18px;
+  color: #e9f4fb;
+  font-weight: 700;
+  cursor: pointer;
+  outline: none;
+}
+input[type="submit"]:hover{
+  border-color: #2691d9;
+  transition: .5s;
+}
+.signup_link{
+  margin: 30px 0;
+  text-align: center;
+  font-size: 16px;
+  color: #666666;
+}
+.signup_link a{
+  color: #2691d9;
+  text-decoration: none;
+}
+.signup_link a:hover{
+  text-decoration: underline;
+}