Theme improvements (#822)

* start converting

* small fixes

* reorganize theme files

* cleanup search bar

* increase spacing

* small tweaks

* fix select styles in Chrome

* cleanup menus

* improve button icons

* restore badges

* remove unused classes

* restore some overrides

* restore bookmark form

* add summary outline

* avoid layout shifts

* restore bookmark details

* increase border radius for modals

* improve details modal

* restore reader mode

* restore settings

* cleanup variables

* start with dark theme

* more dark theme...

* more light theme...

* more dark theme...

* add postcss build

* remove sass processor

* update docker build

* fix alt color

* remove endless symbol

* fix tests

* update assets

* remove sass files

* fix docker build

* cleanup spacing

* improve theme

* update test scripts

* update CI workflow

* fix test

bookmarks/styles/theme/asian.css

@@ -0,0 +1,43 @@
+/* Optimized for East Asian CJK */
+html:lang(zh),
+html:lang(zh-Hans),
+.lang-zh,
+.lang-zh-hans {
+    font-family: var(--cjk-zh-hans-font-family);
+}
+
+html:lang(zh-Hant),
+.lang-zh-hant {
+    font-family: var(--cjk-zh-hant-font-family);
+}
+
+html:lang(ja),
+.lang-ja {
+    font-family: var(--cjk-jp-font-family);
+}
+
+html:lang(ko),
+.lang-ko {
+    font-family: var(--cjk-ko-font-family);
+}
+
+:lang(zh),
+:lang(ja),
+.lang-cjk {
+    & ins,
+    & u {
+        border-bottom: var(--border-width) solid;
+        text-decoration: none;
+    }
+
+    & del + del,
+    & del + s,
+    & ins + ins,
+    & ins + u,
+    & s + del,
+    & s + s,
+    & u + ins,
+    & u + u {
+        margin-left: .125em;
+    }
+}