Update index.d.ts

[kira1928]

Add the optional parameter argsDescription to description() function

[shadowspawn]

@kira1928
Would it be appropriate to have type matching what I think is the expected use:

{{[argName: string]: string}}

rather than the pure object style definition:

{{[key: string]: any}}

[kira1928]

@shadowspawn
Thank you for your advice.
I have fixed the problem you mentioned.
Does it look better now?

[shadowspawn]

Looks good to me. Thanks.

[abetomo]

Thank you!