Use current buffer text in history search

[unrealapex]

Issue:
I am unable to use the text I currently have in the line buffer in history search. When I start history search, the buffer contents are cleared.

Goal:
If the buffer has text already, Yash should use that in history search instead of just clearing it. If there is no text, don't prefill it.

Workarounds or alternatives:
Retyping what I had previously typed in the buffer into the history search prompt.

Environment:

• OS version: 6.15.7-0-generic kernel
• Yash version: 2.59
• Locale: en_US.UTF-8

Additional context:
Other shells with history search will search using the contents of the line buffer if available.

I am willing to try working on this.