`memoryUsageWeigher` missing from exports

[elshize]

Hi, the docs mention memoryUsageWeigher, but I cannot find it in the entire repository except the readme. I looked through some old issues and commits, and looks like it was here at one point, but was left out when moving to TS, but can't be sure why and what happened. Or else the documentation needs to be updated...

[ivan-kleshnin]

It's called memoryEstimator in the latest version. Regardless, this functionality seems to be broken:

.withWeigher((_key, value) => {
    return value.length // setting "json" to cache -> weightedSize = 4
  })

.withWeigher((_key, value) => {
    return 32 // setting "json" to cache -> weightedSize = 0 (not 32)
  })