feat: inject latest QuickFIX/J release version dynamically at build time

[Copilot]

Version strings (3.0.0) were hardcoded across the homepage and docs, requiring manual updates on every release.

How it works

• docusaurus.config.ts — converted to async function createConfig(). Fetches https://api.github.com/repos/quickfix-j/quickfixj/releases/latest at build time, strips the v prefix, falls back to 3.0.0 on any network/API failure. Exposed via customFields.quickfixjVersion and passed into a remark plugin.

• Remark plugin (inline in config) — walks the markdown AST at build time and replaces {{QUICKFIXJ_VERSION}} in text, inlineCode, and code nodes. No new dependencies.

• src/pages/index.tsx — QuickStartSection reads siteConfig.customFields.quickfixjVersion via useDocusaurusContext().

• docs/overview.md, docs/examples.md — hardcoded versions replaced with the {{QUICKFIXJ_VERSION}} placeholder.

Placeholder usage

Editors write the version naturally in markdown:

<dependency>
    <artifactId>quickfixj-core</artifactId>
    <version>{{QUICKFIXJ_VERSION}}</version>
</dependency>

The remark plugin resolves it to the current release at build time.