Show requestor name/mail instead of generic mail

[Bolli84]

Currenty, i get the following mail from libresign:

"File to sign There is a document for you to sign. Access the link below:"

It is not clear, WHO sent me that mail. The NC Account-Name or Mail should be shown and should also be used to answer the mail directly.

[vitormattos]

Could you provide a suggestion about text to be replaced?

Recently I made this:

• https://github.com/LibreSign/libresign/pull/2509

Maybe we can use the same message that I implemented to Activity when is a new sign request:

'{from} requested your signature on {file}'

And this when is about changes at the file:

'{from} made changes on {file}'