Add setResponseTimeout() for configurable response timeout

[karolyczovek]

Description

The response timeout is currently a fixed 2000 ms (ku16MBResponseTimeout). When no slave is present, each request blocks for 2 s, which can make the main loop unresponsive (e.g. serial input lag) when doing multiple reads per cycle.

This change adds setResponseTimeout(uint16_t ms) so the timeout can be set after begin(). Default remains 2000 ms. A private member _u16ResponseTimeoutMs is initialized to ku16MBResponseTimeout in the constructor. Existing code is unchanged; call setResponseTimeout(500) (or similar) to fail sooner when no device responds.

Backward compatible: if setResponseTimeout() is never called, behaviour is identical to before.

Issues Resolved

None (new feature; no existing issue).

Check List

General

• Code follows coding style defined in STYLE.md
• Doxygen comments are included inline with code
• No unnecessary whitespace; check with git diff --check before committing.

The following have been modified to reflect new features, if warranted

• README.md
• keywords.txt (use tabs as whitespace separators)
• library.properties
• examples/ – update or create new ones, as warranted

The following have NOT been modified

• doc/
• .ruby-gemset
• .ruby-version
• CHANGELOG.md
• Gemfile
• LICENSE
• VERSION