rename .svelte to .svelte-kit

[Rich-Harris]

Is your feature request related to a problem? Please describe.
This is a small thing, but sometimes I need to search for a string inside my gitignored files, but I don't want to search inside the .svelte directory. But if I add .svelte to the ignored paths it also excludes all *.svelte files unless I remember to do ./.svelte instead. Been caught out by this a few times and I feel like life would just be simpler if we just changed it to .svelte-kit, which is arguably a better representation of what the directory is for

How important is this feature to you?
Low priority but easy to do