add docusaurus-plugin-copy-page-button

[portdeveloper]

adds docusaurus-plugin-copy-page-button to dependencies and plugins array

what it does: a "Copy page" button in the docs sidebar that exports the current page as clean markdown. also has one-click "Open in Claude / ChatGPT / Gemini" actions that prefill the markdown.

lido-specific angle: the integration guides, contracts pages, and oracle/rewards spec docs all carry a lot of "you need to read 3 surrounding pages" context. when an integrator is on, say, the wstETH or stMATIC integration guide and wants to ask claude "how do I plumb this into my vault contract", the per-page markdown handoff is the right unit — not the whole site, not a manually-pasted snippet that drops the context.

auto-injects into the TOC sidebar. theme-aware. ~5kb client. no config required.

shipping on Ethereum execution-apis, Sui, Walrus, Seal, SuiNS, Monad, Flare, Kaia, Nillion, Chronicle, Cardano and Arbitrum docs. listed in the Docusaurus community plugins page.

repo: https://github.com/portdeveloper/docusaurus-plugin-copy-page-button
npm: https://www.npmjs.com/package/docusaurus-plugin-copy-page-button (~10k installs/mo)
demo: https://portdeveloper.github.io/copy-page-button-showcase/

happy to close/rebase if not a fit

[karinamaulitova]

Really appreciate the effort on this, thank you! We already have our own tooling in place for this, and we're trying to keep our supply chain lean, so we won't be merging. Thanks again for the contribution.