Rayon parallelization?

[HerringtonDarkholme]

The experimentation shows that rayon has at least 100us overhead for thread pool initialization.
However, most template can be compiled within 100us. The parallelization, at least in practice, does not pay off.

The example is the most complicated SFC in element-plus, el-table.vue. The compilation takes about 100us without thread pool.

But after the thread pool is introduced the compilation time comes to 200us+.