DNS provider API: structured description

Instead of using comments declare info in a special variable.
Then the variable can be used to print the DNS API provider usage.
The usage can be parsed on UI and show all needed inputs for options.

The info is stored in plain string that it's both human-readable and easy to parse:

    dns_example_info='API name
     An extended description.
     Multiline.
    Domains: list of alternative domains to find
    Site: the dns provider website e.g. example.com
    Docs: Link to ACME.sh wiki for the provider
    Options:
     VARIABLE1 Title for the option1.
     VARIABLE2 Title for the option2. Default "default value".
     VARIABLE3 Title for the option3. Description to show on UI. Optional.
    Issues: Link to a support ticket on https://github.com/acmesh-official/acme.sh
    Author: First Lastname <authoremail@example.com>, Another Author <https://github.com/example>;
    '

Here:
VARIABLE1 will be required.
VARIABLE2 will be required too but will be populated with a "default value".
VARIABLE3 is optional and can be empty.

A DNS provider may have alternative options like CloudFlare may use API KEY or API Token.
You can use a second section OptionsAlt: section.

Some providers may have alternative names or domains e.g. Aliyun and AlibabaCloud.
Add them to Domains: section.

Signed-off-by: Sergey Ponomarev <stokito@gmail.com>

dnsapi/dns_mydnsjp.sh

@@ -1,14 +1,14 @@
 #!/usr/bin/env sh
+# shellcheck disable=SC2034
+dns_mydnsjp_info='MyDNS.JP
+Site: MyDNS.JP
+Docs: github.com/acmesh-official/acme.sh/wiki/dnsapi#dns_mydnsjp
+Options:
+ MYDNSJP_MasterID Master ID
+ MYDNSJP_Password Password
+Author: epgdatacapbon
+'
 
-#Here is a api script for MyDNS.JP.
-#This file name is "dns_mydnsjp.sh"
-#So, here must be a method   dns_mydnsjp_add()
-#Which will be called by acme.sh to add the txt record to your api system.
-#returns 0 means success, otherwise error.
-#
-#Author: epgdatacapbon
-#Report Bugs here: https://github.com/epgdatacapbon/acme.sh
-#
 ########  Public functions #####################
 
 # Export MyDNS.JP MasterID and Password in following variables...