fix: template specializations in ArtnetWiFi.h cause multiple definition linker errors in multi-file C++ projects (v0.9.1)

[costyn]

Hello again,

I've been running into a linker issue, when using the 0.9.1 in my C++ project.

Below is the analysis of Claude Code, please take it with a grain of salt, it could be garbage and I'm doing it wrong. If so, my apologies. But, adding the inline keywords fixes the issue for my build.

Thank you for a cool library!

---

The template specializations for getLocalIP, getSubnetMask, getMacAddress, and isNetworkReady in ArtnetWiFi.h (lines 102, 108, 114, 120) (and the other .h files) are missing the inline keyword, causing ODR (One Definition Rule) violations when the header is included in multiple translation units.

Error Example:

multiple definition of `IPAddress art_net::getLocalIP<WiFiUDP>()'

Affected Code (ArtnetWiFi.h):

template <>
IPAddress getLocalIP<WiFiUDP>()  // <-- Missing 'inline'
{
    return LocalIP<ArtnetWiFiClass>::get(WiFi);
}

Fix: Add inline keyword to all four template specializations (lines 102, 108, 114, 120):

template <>
inline IPAddress getLocalIP<WiFiUDP>()
{
    return LocalIP<ArtnetWiFiClass>::get(WiFi);
}

Why this happens:
Simple Arduino sketches (single .ino file) work fine because they compile to one translation unit
Multi-file C++ projects fail because the template specializations get compiled into multiple object files
The linker sees duplicate symbols and fails

Impact of fix:
✅ No behavior change for existing working code
✅ No performance impact
✅ Fixes multi-file C++ projects (PlatformIO, Arduino with multiple .cpp files)
✅ Standard C++ practice for header-only template specializations

[hideakitai]

Good point. LGTM