Extract watermark into plugin

[SlicedSilver]

Type of PR: enhancement

PR checklist:

• Includes tests
• Documentation update

Overview of change:

• Removes the watermark feature from the core library and instead implements it as a built-in Pane Primitive (a.k.a plugin). This allows the watermark feature to be tree-shaken if not used.
• Two new plugins included with the library build: TextWatermark and ImageWatermark
• TextWatermark extends the behaviour of the old watermark feature by supporting multiple lines of text
• ImageWatermark adds the ability to easily add an image watermark.
• Both plugins work with the new Pane Primitive.

[github-actions]

size-limit report 📦

Path	Size
ESM	43.07 KB (+1.44% 🔺)
ESM createChart	41.76 KB (-1.12% 🔽)
ESM createChartEx	40.49 KB (-0.99% 🔽)
Standalone-ESM	0 B (-100% 🔽)
Standalone	44.53 KB (+1.46% 🔺)
ESM Standalone	44.53 KB (+100% 🔺)
Plugin: Text Watermark	1.79 KB (+100% 🔺)
Plugin: Image Watermark	1.7 KB (+100% 🔺)

[SlicedSilver]

size-limit report 📦

Path Size
ESM 43.07 KB (+1.44% 🔺)
ESM createChart 41.76 KB (-1.12% 🔽)
ESM createChartEx 40.49 KB (-0.99% 🔽)
Standalone-ESM 0 B (-100% 🔽)
Standalone 44.53 KB (+1.46% 🔺)
ESM Standalone 44.53 KB (+100% 🔺)
Plugin: Text Watermark 1.79 KB (+100% 🔺)
Plugin: Image Watermark 1.7 KB (+100% 🔺)

FYI: I renamed Standalone-ESM to ESM Standalone