docs: fix dead links to d1 platform directories #919

Job	Run time
netlify_dryrun	2m 39s
just check	4m 22s
just clippy	4m 51s
docs	2m 34s
rustfmt	21s
just test	2m 10s
cargo miri test --package forth3 (host)	1m 20s
cargo build mnemos-d1	1m 33s
cargo build mnemos-esp32c3-buddy	58s
cargo build mnemos-x86_64-bootloader	2m 16s
all systems go!	1s
	23m 5s

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