Consolidate vignettes into pattern families

[trevorld]

v0.2 of {ggpattern} has built-in support for eight new patterns:

• "ambient" (the suggested package {ambient} must be installed)
• "pch"
• "polygon_tiling"
• "regular_polygon"
• "rose"
• "text"
• "wave"
• "weave"

Not sure we need separate vignettes for all new patterns... Maybe consolidate into a few vignette pattern "families":

"stripe" family:

• stripe
• crosshatch
• weave
• wave

"circle" family:

• circle
• regular_polygon
• rose
• pch
• text?

"image" family:

• image
• placeholder

Plus five more without such a clear "family"

• polygon_tiling
• gradient
• magick
• plasma
• ambient