build(docker): add docs build dockerfile

Author: nickmessing

packages/private/docs/Dockerfile

@@ -0,0 +1,13 @@
+FROM node:21-slim AS base
+ENV PNPM_HOME="/pnpm"
+ENV PATH="$PNPM_HOME:$PATH"
+RUN corepack enable
+COPY . /app
+WORKDIR /app
+
+FROM base AS build
+RUN --mount=type=cache,id=pnpm,target=/pnpm/store pnpm install --frozen-lockfile
+RUN pnpm run build:docs
+
+FROM base
+COPY --from=build /app/packages/private/docs/.vitepress/dist /app/packages/private/docs/.vitepress/dist