doc: update README.md

README.md

@@ -31,6 +31,7 @@ Example usage:
 --grid              Grid mode (sets position for each character)
 --help, -h          Show help
 --listcolorschemes  List color schemes
+--marginsize WxH    Margin size (in either pixel or font units)
 --transparent       Transparent background
 --version, -v       Show version
 --width, -w NUMBER  Terminal width (auto if not set)
@@ -75,6 +76,11 @@ By default, `ansisvg` uses font-relative `ch`/`em` coordinates. This should make
 
 Inkscape currently [cannot deal with SVG size expressed in font-relative units](https://gitlab.com/inkscape/inkscape/-/issues/4737), a quick workaround is Ctrl-Shift-R (resize page to content).
 
+## Margin size
+
+With `--marginsize` a margin can be defined, so there is a bit of empty space (or "border") around the image. Default is zero margin size, i.e. the terminal characters are touching the edge of the image.
+`--marginsize` is interpreted as X/Y in the currently selected units, i.e. `ch`/`em` by default, and `px` if `--charboxsize` is used.
+
 ## Consolidated text vs. grid mode
 
 By default, `ansisvg` consolidates text to `<tspan>` chunks, leaving the X positioning of characters to the SVG renderer. This usually works well for monospace fonts. However if not all glyphs involved are monospace (e.g. when exotic characters are used, making the SVG renderer fall back to a different font for those characters) then the alignment will be off; this can be worked around with `-grid` mode which will make `ansisvg` put each character to explicit positions, making the SVG bigger and less readable but ensuring proper positioning/alignment for all characters.