Use registered username in template

[Siddhant-K-code]

• Check if an user has registered on Codemon, by checking if meta.json file exists in ~/.codemon.
• If user is registered, use the username defined in meta.json in the templates
• If user is not registered, use "@ankingcodes" as default username

[ankushbhardwxj]

@Siddhant-K-code - Go ahead & make a PR for it.