Translate please https://rcore-os.github.io/rCore_tutorial_doc/ in English

Following the step of @wangrunji0408, I want to port the tutorial from Qemu to K210, a RISC-V board which is cheap and simple, as an important part of the fourth edition of tutorial.
K210 is based on RISC-V spec 1.9.1, which was published about 4 years ago. So you can hardly find a toolchain or bootloader that fits it perfectly now. For example, OpenSBI 0.4/0.8 don't work normally on K210...
About 1 year and a half ago, rjgg tried to port rCore to K210 and succeed in the end. Here is his log. He modified OpenSBI 0.3 in order to support K210, you can find that version here.
How to use it to completing porting? It is at a relative ease. First, download the modified OpenSBI, and change the FW_PAYLOAD_ALIGN to 0x200000 since we want to put our kernel to 0x80200000 on memory. Then, merge the OpenSBI image(fw_payload.bin) and our kernel image into a big one using dd tool and finally burn it into flash.
Now, chapter 2 can run on K210 successfully. I will create a new branch about porting later.

Sometimes kernel panicked when typing commands in the user shell, the following two errors could be found in the panic infomation:

panicked at 'called `Option::unwrap()` on a `None` value', src/process/processor.rs:100:40
panicked at 'thread not exist!', src/process/thread_pool.rs:49:31

Maybe there are some bugs in the scheduling module or the thread management module.

Hi,thank-you for the rcore-tutorial. I noticed that rcore v3 uses the GPL3 license and I was wondering if you forgot to add a license to rcore v2

make run on master branch, and it panicked with:

Exception(StorePageFault) va = 0xffffffffffffffe8 instruction = 0x1acfe
panicked at 'page fault!', src/interrupt.rs:76:5

• rust-toolchain = nightly-2020-06-04
• riscv = 21e32ee
  In the meanwhile, multicore branch worked normally 15 days ago, but now it failed with page fault too. Given that the only change of it in the last two weeks was the update of riscv crate, so I think there maybe some bugs in it. Actually, I made it work again by rolling back the riscv version to c62af46.