Make html formatting configurable

[hellux]

possibly a slight performance hit on renderer but overall it is mostly unaffected

model name	: AMD Ryzen 9 5950X 16-Core Processor
commit                                                   criterion:full/readme [MB/s]  criterion:html/readme [MB/s]
8ebed5be6 lib: include type of char used for list items  109.41                        40.392
b42d68976 block: fix blockquote code block indent        107.07                        40.460
a41fa2996 html: add optional minified formatting         104.90                        36.755
0ed21b590 html: add optional indented formatting         112.60                        39.880
d260fb2c1 html: make initial indent level configurable   107.28                        38.868

[dcampbell24]

This looks good!