Updated DNS API Dev Guide (markdown)

DNS-API-Dev-Guide.md

@@ -1 +1,30 @@
 Guide for developing a dns api for acme.sh
+
+Let's assume your api name is `myapi`, and you will use your api like:
+
+```sh
+export MYAPI_Username=myname
+export MYAPI_Password=mypass
+acme.sh --issue -d example.com  --dns  dns_myapi
+
+```
+
+Here we go:
+
+#### 1. The cloudflare dns api is a recommended reference:
+
+https://github.com/Neilpang/acme.sh/blob/master/dnsapi/dns_cf.sh
+
+#### 2. The script file name must be `myapi.sh`
+The file name must be in this format: `yourApiName.sh`, in this example, it should be `myapi.sh`
+
+#### 3. The file can be placed in `acme.sh/` folder, or in `acme.sh/dnsapi/` subfolder.
+If you want to contribute your script to `acme.sh` project,  it must be placed in `acme.sh/dnsapi/` folder.
+
+If you just want to use your script on your machine, you can put it in `.acme.sh/` or `.acme.sh/dnsapi/` folders.
+acme.sh searches the script files in either the  acme.sh home dir(`.acme.sh/`) or in the  `dnsapi` subfolder(`.acme.sh/dnsapi`).
+
+#### 4. 
+
+
+