docs(README) Update minimum tmux version to 3.2+

Reflects the minimum version bump in v1.57.0 via libtmux 0.48.0.

Author: tony

README.md

@@ -293,7 +293,7 @@ See donation options at <https://tony.sh/support.html>.
 
 # Project details
 
-- tmux support: 1.8+
+- tmux support: 3.2+
 - python support: >= 3.10, pypy, pypy3
 - Source: <https://github.com/tmux-python/tmuxp>
 - Docs: <https://tmuxp.git-pull.com>