exercises/src/topics.md

Topics

Rows are ordered based on estimated difficulty.

lifetimes[-adjacent]	traits	structs
explicit lifetimes	Fn?	Duration
from reference	async Fn	All Errors?
extracting lifetimes	exclusive traits	RcChars
composition	merging traits	AnyStr

p.s. most of the exercises are actually about traits, this categorisation isn't strict.