Merge branch 'canary' into master (#711)

* refactor(i18n): simplify the structure of the translation file

* chore: prepare repository for v4.0.0-alpha

* chore: modify go.mod to v4

* refactor: migrate theme configuration to TOML

* fix: exampleSite not using correct theme

* feat: add favicon from assets folder

* refactor: drop linear grandient background feature

remove node-vibrant from dependencies

* feat: use Hugo's code block render hook to implement code copy button

Now it can have i18n support

* refactor: delete color.ts

* refactor: delete Emoji support post from example site

* refactor: drop support for `hidden` field in front matter

* feat: upgrade to PhotoSwipe v5

* chore: bump the required hugo version to 0.100.0

* refactor: remove PhotoSwipe from external.yaml

* fix: extra margin in search result

* fix: incorrect markdown heading level in example site

* refactor: remove some usages of `default` in template

No longer needed thanks to Hugo's configuration merge

* fix: one line codeblock style in firefox

closes https://github.com/CaiJimmy/hugo-theme-stack/issues/564

* feat: add style to new codeblock

* feat: i18n support for codeblock copy text

* fix(menu): jitter when closing menu

It's caused by flexbox gap property, which can't animate

* fix(search): long text overflows under the Search icon

closes https://github.com/CaiJimmy/hugo-theme-stack/issues/515

exampleSite/content/post/emoji-support/index.md

@@ -1,50 +0,0 @@
-+++
-author = "Hugo Authors"
-title = "Emoji Support"
-date = "2019-03-05"
-description = "Guide to emoji usage in Hugo"
-categories = [
-    "Test"
-]
-tags = [
-    "emoji",
-]
-image = "the-creative-exchange-d2zvqp3fpro-unsplash.jpg"
-+++
-
-Emoji can be enabled in a Hugo project in a number of ways. 
-<!--more-->
-The [`emojify`](https://gohugo.io/functions/emojify/) function can be called directly in templates or [Inline Shortcodes](https://gohugo.io/templates/shortcode-templates/#inline-shortcodes). 
-
-To enable emoji globally, set `enableEmoji` to `true` in your site's [configuration](https://gohugo.io/getting-started/configuration/) and then you can type emoji shorthand codes directly in content files; e.g.
-
-<p><span class="nowrap"><span class="emojify">🙈</span> <code>:see_no_evil:</code></span>  <span class="nowrap"><span class="emojify">🙉</span> <code>:hear_no_evil:</code></span>  <span class="nowrap"><span class="emojify">🙊</span> <code>:speak_no_evil:</code></span></p>
-<br>
-
-The [Emoji cheat sheet](http://www.emoji-cheat-sheet.com/) is a useful reference for emoji shorthand codes.
-
-***
-
-**N.B.** The above steps enable Unicode Standard emoji characters and sequences in Hugo, however the rendering of these glyphs depends on the browser and the platform. To style the emoji you can either use a third party emoji font or a font stack; e.g.
-
-{{< highlight html >}}
-.emoji {
-  font-family: Apple Color Emoji, Segoe UI Emoji, NotoColorEmoji, Segoe UI Symbol, Android Emoji, EmojiSymbols;
-}
-{{< /highlight >}}
-
-{{< css.inline >}}
-<style>
-.emojify {
-	font-family: Apple Color Emoji, Segoe UI Emoji, NotoColorEmoji, Segoe UI Symbol, Android Emoji, EmojiSymbols;
-	font-size: 2rem;
-	vertical-align: middle;
-}
-@media screen and (max-width:650px) {
-  .nowrap {
-    display: block;
-    margin: 25px 0;
-  }
-}
-</style>
-{{< /css.inline >}}