Changes ESLint warning message to still encourage usage of `next/image`
for the best experience, but also denoting that optimization could come
with incurred costs.
## Feature
- [x] Documentation added
- [x] Errors have a helpful link attached, see
[`contributing.md`](https://github.com/vercel/next.js/blob/canary/contributing.md)
## Documentation / Examples
- [x] Make sure the linting passes by running `pnpm build && pnpm lint`
- [x] The "examples guidelines" are followed from [our contributing
doc](https://github.com/vercel/next.js/blob/canary/contributing/examples/adding-examples.md)
---------
Co-authored-by: Steven Tey <stevensteel97@gmail.com>
Co-authored-by: Steven <steven@ceriously.com>
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