Make click-header export $FZF_CLICK_HEADER_{NTH,WORD}

CHANGELOG.md

@@ -14,6 +14,18 @@ CHANGELOG
                --bind 'ctrl-r:reload(ps -ef)' --header 'Press CTRL-R to reload' \
                --header-lines-border bottom --no-list-border
   ```
+- `click-header` event will also set `$FZF_CLICK_HEADER_WORD` and `$FZF_CLICK_HEADER_NTH`. You can use it to implement a clickable header that changes the search scope using the new `transform-nth` action.
+  ```sh
+  # Click on the header line to limit search scope
+  ps -ef | fzf --style full --layout reverse --header-lines 1 \
+               --header-lines-border bottom --no-list-border \
+               --color fg:dim,nth:regular \
+               --bind 'click-header:transform-nth(
+                         echo $FZF_CLICK_HEADER_NTH
+                       )+transform-prompt(
+                         echo "$FZF_CLICK_HEADER_WORD> "
+                       )'
+  ```
 - Added `search(...)` and `transform-search(...)` action to trigger an fzf search with an arbitrary query string. This can be used to extend the search syntax of fzf. In the following example, fzf will use the first word of the query to trigger ripgrep search, and use the rest of the query to perform fzf search within the result.
   ```sh
   TRANSFORMER='