More dev friendly errors

[vikiival]

It would be nicer to throw away errors that are more user friendly

This one could be "unable to perform fetch for non-existing indexer, add parameter prefix when calling getClient"

ht/ @poppyseedDev

[roiLeo]

Indexer not found when no client set, shoudl fallback to smething default

[vikiival]

shoudl fallback to smething default

and It would return undefined if you provide bad params.

We can either implement:

• use path also for client instance #16
  or
• log warn wen client is not supplied

[roiLeo]

or add it to readme (or jsdoc) so devs won't loose time debuging this one

[vikiival]

or add it to readme (or jsdoc) so devs won't loose time debuging this one

added 1764cf0