Fix typos in thread-pool.h
/// @page
///
-/// This extension let the plugin use the host's thread pool.
+/// This extension lets the plugin use the host's thread pool.
///
/// The plugin must provide @ref clap_plugin_thread_pool, and the host may provide @ref
-/// clap_host_thread_pool. If it doesn't, the plugin should process its data by its own mean. In the
+/// clap_host_thread_pool. If it doesn't, the plugin should process its data by its own means. In the
/// worst case, a single threaded for-loop.
///
/// Simple example with N voices to process
