UPDATE: Adds web app (#79)

Things missing:

* Browse mode
* Front end tests
* Storybook

base/src/test/user_model/test_on_paste_styles.rs

@@ -0,0 +1,48 @@
+#![allow(clippy::unwrap_used)]
+
+use crate::test::util::new_empty_model;
+use crate::types::Fill;
+use crate::UserModel;
+
+#[test]
+fn simple_pasting() {
+    let model = new_empty_model();
+    let mut model = UserModel::from_model(model);
+    let mut style = model.get_cell_style(0, 1, 1).unwrap();
+    style.fill = Fill {
+        pattern_type: "solid".to_string(),
+        fg_color: Some("#FF5577".to_string()),
+        bg_color: Some("#33FF44".to_string()),
+    };
+    let styles = vec![vec![style.clone()]];
+
+    model.set_selected_cell(5, 4).unwrap();
+    model.set_selected_range(5, 4, 10, 9).unwrap();
+    model.on_paste_styles(&styles).unwrap();
+
+    for row in 5..10 {
+        for column in 4..9 {
+            let cell_style = model.get_cell_style(0, row, column).unwrap();
+            assert_eq!(cell_style, style);
+        }
+    }
+
+    model.undo().unwrap();
+    let base_style = model.get_cell_style(0, 100, 100).unwrap();
+
+    for row in 5..10 {
+        for column in 4..9 {
+            let cell_style = model.get_cell_style(0, row, column).unwrap();
+            assert_eq!(cell_style, base_style);
+        }
+    }
+
+    model.redo().unwrap();
+
+    for row in 5..10 {
+        for column in 4..9 {
+            let cell_style = model.get_cell_style(0, row, column).unwrap();
+            assert_eq!(cell_style, style);
+        }
+    }
+}