meta: update to babel 7

[WikiRik]

This should not change any functionality, but I haven't tested the built code on the browser or with a low Node version. Therefore it's still in draft.

This brings us to the question of supported versions. The original has browser support and test on Node 10, although I think it has support for versions below that. What versions do we want to support? Just go with Node ^14.17.0 || >=16.0.0 like for sequelize or do we want to keep the support for browser/old Node versions? With babel this should not be too difficult I think, but we'll have to add CI for it. @ephys any preference?

[ephys]

Do you think it's worth it to use babel VS rewriting in TS and using TSC?

[WikiRik]

I just used babel since it was already using that but using tsc should also be fine. I think however that the question does remain; do we want to keep supporting old browsers and old Node versions or keep the same version support as sequelize v7?

[ephys]

The same as sequelize, we don't need to support dead versions of node (and it should be fine for browsers, users always have the option to transpile the library if they need to support old browsers)

[WikiRik]

Then I'll use tsc in this project as well. New PR for that will follow soonish