chore(release): prepare v0.2.0

[tappe9]

Summary

• bump the workspace version to 0.2.0
• update the English and Japanese README release links and dependency examples
• mark the v0.2 roadmap scope as released and defer remaining candidates

Verification

• cargo fmt --check
• cargo clippy --workspace --all-targets --all-features --locked -- -D warnings
• cargo test --workspace --all-features --locked
• RUSTDOCFLAGS=-D warnings cargo doc -p zstdscope --all-features --no-deps --locked
• cargo test -p zstdscope --no-default-features --locked
• cargo publish -p zstdscope --dry-run --locked
• cargo +1.85.0 check/test --workspace --all-targets --all-features --locked