Implements image rendering using indexed-color SGR control sequences to support terminal emulators without direct-color SGR (truecolor) support.
Adds DIRECT and INDEXED render methods for BlockImage.
Adds method style-specific render parameter and format spec field for BlockImage.
Implements image quantization for text-based render styles.
Updates terminal support information.
Resolves #90
Partially addresses #61
[!NOTE]
This is just an implementation to satisfy demand in the meantime, while we await full resolution of #61.
For this reason, this will only be merged into v0.7.x and not main.
DIRECTandINDEXEDrender methods forBlockImage.BlockImage.Resolves #90 Partially addresses #61