feat: add zsh-autosuggestions and zsh-syntax-highlighting (#14088)

Closes #12865
Closes #11995
Closes #12864

plugins/zsh-syntax-highlighting/docs/highlighters/root.md

@@ -0,0 +1,25 @@
+zsh-syntax-highlighting / highlighters / root
+---------------------------------------------
+
+This is the `root` highlighter, that highlights the whole line if the current
+user is root.
+
+
+### How to tweak it
+
+This highlighter defines the following styles:
+
+* `root` - the style for the whole line if the current user is root.
+
+To override one of those styles, change its entry in `ZSH_HIGHLIGHT_STYLES`,
+for example in `~/.zshrc`:
+
+```zsh
+ZSH_HIGHLIGHT_STYLES[root]='bg=red'
+```
+
+The syntax for values is the same as the syntax of "types of highlighting" of
+the zsh builtin `$zle_highlight` array, which is documented in [the `zshzle(1)`
+manual page][zshzle-Character-Highlighting].
+
+[zshzle-Character-Highlighting]: https://zsh.sourceforge.io/Doc/Release/Zsh-Line-Editor.html#Character-Highlighting