Update install.sh (add TencentCloud download url)

[89ao]

add TencentCloud download url

- What I did add TencentCloud download url

- How I did it add TencentCloud download url(https://mirrors.cloud.tencent.com) in the install.sh

- How to verify it curl -fsSL https://get.docker.com -o get-docker.sh sudo sh get-docker.sh --mirror TencentCloud

- Description for the changelog

Add the download address of TencentCloud to facilitate faster use by users within certain networks.

- A picture of a cute animal (not mandatory but encouraged)

[89ao]

Excuse me ,please help me check this request,thank you guys !@nicksieger @jgdavey @SvenDowideit @shykes

[VAllens]

Thanks for contributing; I don't think we want to add more options to this list; the original list of mirrors were part of some partnerships (but those ended, so we may even consider removing those).

If you need to use a custom / alternative mirror, I would recommend using the env-var when executing the script.DOWNLOAD_URL

I was planning to add TencentCloud as a mirror option and pull request. So I found this place, and after seeing your comment, I realized that I've been using get-docker.sh for so long and never knew about the DOWNLOAD_URL environment variable. This is great idea.