Add react-i18next for multi-language support (#917)

This is a rough start on adding react-i18next. I'll be working on adding
more translatable strings and translations in the coming days. I'm going
to need to wrap class components in HOCs, so let me know if there's
something I should be fixing before doing that. I'm thinking now to keep
the exported class names exactly the same, and rename the existing
classes by prefixing an `I` (for internal). For example:

```
export default class AppToolbar ...
```

becomes

```
class IAppToolbar ...
const AppToolbar = withTranslation()(IAppToolbar);
export default AppToolbar;
```

I'll be able to contribute Japanese strings (I've talked to a couple
people on my team and they'll be happy to help as well), so that's the
language I decided to go with in this PR.

Closes #746

---------

Co-authored-by: Ko Nagase <nagase@georepublic.co.jp>
Co-authored-by: Harel M <harel.mazor@gmail.com>

src/styles/_components.scss

@@ -3,11 +3,6 @@
 .maputnik-map__container {
   background: white;
   display: flex;
-  position: fixed !important;
-  top: $toolbar-height + $toolbar-offset;
-  right: 0;
-  bottom: 0;
-  height: calc(100% - #{$toolbar-height + $toolbar-offset});
   width: $layout-map-width;
 
   &--error {

src/styles/_layout.scss

@@ -14,26 +14,28 @@
   font-family: $font-family;
   color: $color-white;
 
-  &-list {
+  &-main {
     position: fixed;
     bottom: 0;
     height: calc(100% - #{$toolbar-height + $toolbar-offset});
     top: $toolbar-height + $toolbar-offset;
     left: 0;
+    right: 0;
     z-index: 3;
+
+    display: flex;
+  }
+
+  &-list {
     width: 200px;
     background-color: $color-black;
   }
 
   &-drawer {
-    position: fixed;
-    bottom: 0;
-    height: calc(100% - #{$toolbar-height + $toolbar-offset});
-    top: $toolbar-height + $toolbar-offset;
-    left: 200px;
-    z-index: 1;
     width: 370px;
     background-color: $color-black;
+    // scroll-container is position: absolute
+    position: relative;
   }
 
   &-bottom {

src/styles/_modal.scss

@@ -308,26 +308,6 @@
   }
 }
 
-.maputnik-modal-survey {
-  width: 400px;
-}
-
-.maputnik-modal-survey__logo {
-  display: block;
-  margin: 0 auto;
-  height: 128px;
-  width: 128px;
-}
-
-.maputnik-modal-survey__description {
-  line-height: 1.5;
-}
-
-.maputnik-modal-survey__footnote {
-  color: $color-green;
-  margin-top: 16px;
-}
-
 .modal-settings {
   width: 400px;
 }