docs: Replace obsolete <a name> anchor with <a id> in docker/README.md

[coderabbitai]

Summary

The docker/README.md file uses an obsolete HTML anchor attribute (name) for the Spanish section anchor:

<a name="espanol-section"></a>

This should be replaced with the modern id attribute:

<a id="espanol-section"></a>

Why

• <a name="..."\> is obsolete in HTML5 and causes reliability issues in Markdown renderers.
• GitHub applies security prefixing that can break custom name anchors.
• VSCode Markdown preview fails to resolve name anchors.
• Using id ensures consistent link resolution across platforms and renderers.

Reference

Flagged during code review in PR #61: #61 (comment)

Requested by @Delgado74.