feat(leptos_config): only enable `toml` feature for the `config` depe… #871

Job	Run time
get-leptos-changed / Detect Source Change	7s
CI (integrations/actix) / Run ci (nightly)	19m 50s
CI (integrations/axum) / Run ci (nightly)	19m 40s
CI (integrations/utils) / Run ci (nightly)	18m 48s
CI (leptos) / Run ci (nightly)	1h 16m 3s
CI (integrations/viz) / Run ci (nightly)	19m 33s
CI (leptos_config) / Run ci (nightly)	14m 40s
CI (leptos_dom) / Run ci (nightly)	29m 0s
CI (leptos_hot_reload) / Run ci (nightly)	20m 39s
CI (leptos_macro) / Run ci (nightly)	34m 31s
CI (leptos_reactive) / Run ci (nightly)	37m 2s
CI (leptos_server) / Run ci (nightly)	26m 35s
CI (meta) / Run ci (nightly)	22m 37s
CI (router) / Run ci (nightly)	16m 58s
CI (server_fn) / Run ci (nightly)	15m 22s
CI (server_fn_macro) / Run ci (nightly)	15m 25s
CI (server_fn/server_fn_macro_default) / Run ci (nightly)	17m 36s
	6h 44m 26s

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