refactor(host): Group capability slices under src/main/. #16

Job	Run time
Compiler / Lint and Check	28s
Runtime / Deno Lint	6s
CLI / Lint and Check	1m 5s
Compiler / Test and Release	1m 10s
CLI / Release (x86_64-apple-darwin)	3m 23s
CLI / Release (x86_64-unknown-linux-musl)	2m 32s
CLI / Release (aarch64-unknown-linux-musl)	2m 45s
CLI / Release (aarch64-apple-darwin)	3m 54s
Runtime / Deno Test	24s
Std / re	1m 12s
Host / network	34s
Std / test	1m 0s
Host / time	30s
Std / json	1m 15s
Host / storage	24s
Host / dom	31s
Std / math	1m 14s
CLI / Test	1m 46s
Docs / Build	51s
Cloudflare Upload (CDN)	27s
Demo	9s
Docs / Deploy	1s
	25m 41s

Provide feedback