Published version on npm is not same as in repo

`index.js` in the repository has an extra `?` in the exact string interpolation, causing them to validate different things.

Published version: https://cdn.jsdelivr.net/npm/base64-regex@2.0.0/index.js
In repository: https://github.com/kevva/base64-regex/blob/0f0065cb1a1c75dc13c603c424f19103a2294782/index.js

I believe neither of the versions to be correct though, since the `?` should be present in the regex for both exact and non-exact in order to match all base64 strings. Without it, it only matches 2/3 of all possible base64 strings.

Start with index.js and compare the repository implementation with the published npm version linked in the issue. Check the exact and non-exact regular expressions against base64 strings, including cases that require the `?`; done means both versions agree and match all intended base64 strings.

Written by the indexing model from the issue text.