fix(docs): clean up npm search docs

[wraithgar]

In which the "note on caching" is finally populated after
all these years

References

Closes npm/statusboard#243

[npm-deploy-user]

no statistically significant performance changes detected

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	46.017 ±0.19	29.094 ±0.22	31.304 ±1.02	28.105 ±0.97	2.202 ±0.02	2.157 ±0.05	1.542 ±0.04	11.171 ±0.21	1.568 ±0.06	3.528 ±0.04
#2487	47.581 ±1.10	27.791 ±0.18	30.380 ±0.66	29.941 ±0.52	2.233 ±0.01	2.258 ±0.01	1.623 ±0.02	11.787 ±0.31	1.564 ±0.01	3.670 ±0.17

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	32.726 ±0.05	20.659 ±0.64	20.716 ±0.78	19.676 ±0.43	2.067 ±0.00	2.069 ±0.04	1.449 ±0.02	7.042 ±0.04	1.416 ±0.02	3.049 ±0.34
#2487	33.318 ±0.76	20.614 ±0.30	21.965 ±0.29	20.769 ±0.43	2.170 ±0.07	2.129 ±0.01	1.471 ±0.01	7.436 ±0.00	1.548 ±0.02	2.912 ±0.02