Fix Mermaid diagram rendering

[liamaharon]

Closes #2977

The issue appears to stem from the aquamarine crate failing to render diagrams in re-exported crates.

e.g. as raised here, diagrams would render at frame_support::traits::Hooks but not the re-exported doc frame::traits::Hooks, even if I added aquamarine as a frame crate dependency.

To resolve this, I followed advice in mersinvald/aquamarine#20 to instead render mermaid diagrams directly using JS by adding an after-content.js.

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Also fixes compile warnings, enables --all-features and disallows future warnings in CI.

[bkchr]

But this will still fail on docs.rs?

We should think on how to fix this there as well. Setting RUSTDOCFLAGS is also possible: https://github.com/rust-lang/docs.rs/blob/8b19841b449244d79976c29ae24534af3d7e8c82/templates/core/Cargo.toml.example#L42

[liamaharon]

But this will still fail on docs.rs?

We should think on how to fix this there as well. Setting RUSTDOCFLAGS is also possible: https://github.com/rust-lang/docs.rs/blob/8b19841b449244d79976c29ae24534af3d7e8c82/templates/core/Cargo.toml.example#L42

Would we need to set RUSTDOCFLAGS and include the after script in every crate? Maybe it's easier to open an issue downstream in the aquamarine crate and try get it fixed there..

[liamaharon]

So this pr doesn't break crates.io and we can merge it I'm going to restore the aquamarine crate and use it alongside the new after-content script.

[kianenigma]

docs.rs

fwiw we have generally broader issues with docs.rs, especially with publishing polkadot-sdk-docs crate, see: sam0x17/docify#22

It might then therefore be a better tradeoff to say for now we only focus on self-hosted rust docs.

[liamaharon]

Confirmed fixed in prod 🥳 https://paritytech.github.io/polkadot-sdk/master/polkadot_sdk_frame/traits/trait.Hooks.html