fix(docs): add caching docs to exec, init

[wraithgar]

also fix grammar on caching docs for search

[npm-deploy-user]

found 1 benchmarks with statistically significant performance improvements

• app-large: cache-only

timing results

app-large	clean	lock-only	cache-only	cache-only legacy-peer-deps	modules-only	no-lock	no-cache	no-modules	no-clean	no-clean audit
npm@7	47.919 ±1.84	28.090 ±0.03	32.335 ±0.29	30.090 ±1.14	2.235 ±0.04	2.246 ±0.01	1.569 ±0.01	11.594 ±0.10	1.565 ±0.04	4.185 ±0.63
#2542	45.181 ±0.25	28.661 ±0.09	28.951 ±1.00	27.144 ±0.78	2.253 ±0.02	2.268 ±0.00	1.601 ±0.03	11.393 ±0.01	1.604 ±0.01	4.105 ±0.20

app-medium	clean	lock-only	cache-only	cache-only legacy-peer-deps	modules-only	no-lock	no-cache	no-modules	no-clean	no-clean audit
npm@7	34.918 ±0.73	20.345 ±0.06	50.357 ±41.42	21.062 ±0.91	2.085 ±0.01	2.102 ±0.01	1.504 ±0.01	7.197 ±0.06	1.480 ±0.01	3.095 ±0.13
#2542	32.432 ±0.60	20.730 ±0.00	19.700 ±0.06	19.963 ±0.06	2.116 ±0.00	2.131 ±0.01	1.515 ±0.00	7.244 ±0.07	1.501 ±0.02	3.099 ±0.17