Add an example for PRs that don't have anything to prove functionality

Some module submissions don't have a pcap, screenshot/video or anything to prove the module is actually functional or not, often due to the author not having the test box anymore, or unable to share info because of their NDA. We need a way to prove the module actually runs by basically simulating the vulnerable environment live, and this is the answer to that.

This test module is specifically for the cisco_asa_asdm.rb, but future PRs with the same scenario can also borrow the same idea.

Demo:

Test Results - clinet output:

```
msf auxiliary(cisco_asa_asdm) > run

[+] 10.0.1.76:443 - Server is responsive...
[*] 10.0.1.76:443 - Application appears to be Cisco ASA ASDM. Module will continue.
[*] 10.0.1.76:443 - Starting login brute force...
[*] 10.0.1.76:443  - [1/2] - Trying username:"cisco" with password:""
[-] 10.0.1.76:443  - [1/2] - FAILED LOGIN - "cisco":""
[*] 10.0.1.76:443  - [2/2] - Trying username:"cisco" with password:"cisco"
[+] 10.0.1.76:443 - SUCCESSFUL LOGIN - "cisco":"cisco"
[*] Scanned 1 of 1 hosts (100% complete)
[*] Auxiliary module execution completed
msf auxiliary(cisco_asa_asdm) >
```

Test Results - fake server output:

```
msf auxiliary(httpserver) > run

[*] Using URL: https://0.0.0.0:443/
[*]  Local IP: https://10.0.1.76:443/
[*] Server started.
[*] 10.0.1.76        httpserver - Received request: /
[*] 10.0.1.76        httpserver - Received request: /+webvpn+/index.html
[*] 10.0.1.76        httpserver - Responding to the is_app_asdm? method
[*] 10.0.1.76        httpserver - Received request: /+webvpn+/index.html
[-] 10.0.1.76        httpserver - Bad login
[-] 10.0.1.76        httpserver - Exception handling request: wrong number of arguments (1 for 2)
[*] 10.0.1.76        httpserver - Received request: /+webvpn+/index.html
[+] Authenticated
```