[dnsapi] add ServerCore DNS API hook

[kot1grun]

Adds dnsapi/dns_servercore.sh for DNS-01 challenges via ServerCore,

Usage

export SCore_Login_ID=<login_id> # login identifier
export SCore_Project_Name="<project_name>" # project name
export SCore_Login_Name="<username>" # username
export SCore_Pswd="<user_password>" # password for created user

Login identifier can be found in the upper right corner of the control panel.
After that you can issue the certificate with acme.sh, for example:

./acme.sh --issue --dns dns_servercore -d example.net -d *.example.net

Testing

Tested against production ServerCore API with Let's Encrypt staging. Issue and cleanup both work.

[github-actions]

Welcome
READ ME !!!!!
Read me !!!!!!
First thing: don't send PR to the master branch, please send to the dev branch instead.
Please read the DNS API Dev Guide.
You MUST pass the DNS-API-Test.
Then reply on this message, otherwise, your code will not be reviewed or merged.
Please also make sure to add/update the usage here: https://github.com/acmesh-official/acme.sh/wiki/dnsapi2
注意: 必须通过了 DNS-API-Test 才会被 review. 无论是修改, 还是新加的 dns api, 都必须确保通过这个测试.