Add dark mode (#33)

Closes: #18

This PR adds dark mode styling and an app setting to choose light, dark, or auto mode.

Reviewed-on: Georgi_Lab/ALVINN_f7#33

src/css/app.css

@@ -4,16 +4,45 @@
 }
 
 /* Your app custom styles here */
-.view-main {
-  --f7-theme-color: #002F65;
+html {
+  --avn-theme-color: #0f206c;
+  --avn-button-bg-color: #d9d8d6;
+  --avn-structure-box-color: yellow;
 }
 
+.dark {
+  --avn-theme-color: #d9c79e;
+  --avn-button-bg-color: #0f206c;
+}
+
+body {
+  font-family: "Open Sans", sans-serif;
+}
 
 .navbar {
-  --f7-navbar-text-color: #002F65;
-  --f7-navbar-link-color: #002F65;
+  --f7-navbar-text-color: var(--avn-theme-color);
+  --f7-navbar-link-color: var(--avn-theme-color);
 }
 
 .navbar-bg {
-  --f7-navbar-bg-color: #BDBCAF;
-}
+  --f7-navbar-bg-color: #d9c79e;
+}
+
+.dark .navbar-bg {
+  --f7-navbar-bg-color: #0f206c;
+}
+
+/* MWU Colors
+Rich blue: #385cad
+Dark blue: #0f206c
+Light gold: #d9c79e
+Dark gold: #bd9a5f
+
+Secondary:
+White: #ffffff
+Black: #414042
+Dark Gray: #c8c8c8
+Light Gray: #d9d8d6
+Green: #009490
+Purple: #83276b
+*/