Document cleary that the limit configuration is about allocating memory

[LLFourn]

Currently it just says it's a "byte limit" but one could easily assume that it's bytes read rather than bytes allocated while decoding.

[LechintanTudor]

Wait, so the limit isn't the maximum size that an encoded object can have?

[VictorKoenders]

The byte limit is an estimate on how much it would take to keep the decoded structure in memory