Add SvelteKit setup to readme

[vhscom]

Describe the bug
Chromium issues as of late (#68, #69) have obviated a need to note this extension should work out of the box for SvelteKit. Currently there are set-up instructions which do not need to be performed for SvelteKit to function which could cause developer frustration as a result of the bugs (and in general).

Here's the spot that needs rewording or reorg to note SvelteKit works OOTB:
https://github.com/RedHatter/svelte-devtools#enabling-dev-mode