Avatar size parameter added incorrectly to the URL

[Piedone]

Describe the bug
The bot adds avatar images with a size parameter, but that's concatenated incorrectly with a duplicated ?, like this: https://avatars3.githubusercontent.com/u/1976647?v=4?s=100.

To Reproduce

1. Ask the bot to add a contributor of any kind with @all-contributors please add @<username> for <contributions>.
2. Observe that the avatar URL is added with a duplicated ?.

It looks like that this bug has existed forever, our very first contributor profiles under Orchard Core are like this too.

Expected behavior
The s parameter is added with an ampersand instead: https://avatars3.githubusercontent.com/u/1976647?v=4&s=100.

Screenshots
Not applicable.

Additional context
If it affects anything, this is the page we keep up to date: https://docs.orchardcore.net/en/latest/docs/community/contributors/.