Add optional DPI spec for svg2png raster. E.g. " --rasterize --dpi=300 "

[marc-wien]

Legacy behavior does not change if DPI argument is excluded. DPI argument ignored if Rasterize argument excluded.

[marc-wien]

Also want to add example in Quickstart.ipynb after Out[29] but couldn't resolve merging it in easily.

Something like:

Markdown cell:

You can also set the DPI of your raster for print-quality PNG images without modifying the TikZ scale
(Note: you can also set a max render width in a JupyterLab notebook for high-DPI images to force it to fit on screen using the commented-out command in the following cell)

Code cell (intentionally commented out):

# from IPython.core.display import display, HTML
# display(HTML("<style>.jp-RenderedImage img { width: 100%; max-width: 400px }</style>"))

Code cell:

%%itikz --implicit-pic --temp-dir --rasterize --dpi=300
\draw[fill=black] (1, 1) rectangle (2, 2);
\draw[fill=black] (2, 1) rectangle (3, 2);
\draw[fill=black] (3, 1) rectangle (4, 2);
\draw[fill=black] (3, 2) rectangle (4, 3);
\draw[fill=black] (2, 3) rectangle (3, 4);