Function encode_grid 

pub fn encode_grid(grid: &HGrid) -> Result<String, CodecError>

Encode an HGrid to Trio format.

Each row in the grid becomes a record. Records are separated by ---. For each tag in the row:

• Marker values: just the tag name
• Multi-line strings (containing \n): name: then each line indented with 2 spaces
• All other values: name: + zinc-encoded scalar