docs: Fix typos in README.md

[th4ruka]

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Documentation URL

https://github.com/micropython/micropython/blob/master/README.md

Description

I have found a few typos in the README.md. Following is an example,

Select ports have support for _thread module (multithreading), socket and ssl for networking, and asyncio. Note that only a subset of Python 3 functionality is implemented for the data types and modules.

Here, Select should be changed to Selected.
I would like to work on these typos and make a contribution to MicroPython.