(WIP) Adding hash config

[msdrigg]

Adding a function to the configuration to replace stableHash.

This pr is meant to resolve issues discussed in #1846.

It adds a hash function in the configuration that defaults to stableHash.

I haven't written any tests for this, but I have tested this on my personal repository and seen that it works. Can anyone please take a look at this and give me some direction on how to make this ready to merge?

E.g.:

• what tests should I write?
• Am I missing any places I should put the default configuration
• This changes the signature of serialize. Should I make the hash function in serialize optional and make it defualt to stableHash internally?

[msdrigg]

Seeing the errors, and this needs some work. Will resolve issues next week

[psteinroe]

Do you need any support here? :)

[msdrigg]

I have kind of stalled out here. Having a busy week with work and I am out of town this weekend. If anyone wants to take over this, I would not mind at all because I won't be able to get this resolved for at least another week.

There is a lot of work that needs to be done to change the signature of serialize. It might be a better approach to make serialize overridable rather than customHash, but I am not sure if that would work.

[psteinroe]

I have made an attempt here https://github.com/vercel/swr/pull/1940 but a few tests are failing.