Gir uses two types of IR, with and without offsets

Without offsets
---------------
This is produced by `parse`. Each subsection shows the properties the
command object of that type has in IR without offsets

### add
type  | `add`
value | The number to add to current cell

Generated on `+` and `-`

### moveHead
type  | `moveHead`
value | The number of steps to move the tape head right

Generated on `<` and `>`

### writeByte
type | `writeByte`

Generated on `.`

### readByte
type | `readByte`

Generated on `,`

### loop
type     | `loop`
contents | An array of the commands making up the loop body

Generated on `[`…`]`

### clear
type | `clear`

Not generated by the parser directly, but generated by optimizations


With offsets
------------
This is produced by the optimization pass `addOffsetProperties`. Each
subsection shows the properties the command object of that type has in IR
with offsets

### add
type    | `add`
value   | The number to add to the cell
offfset | The location of the cell relative to current tape position

### moveHead
type  | `moveHead`
value | The number of steps to move the tape head right

### writeByte
type   | `writeByte`
offset | The location of the cell relative to current tape position

### readByte
type   | `readByte`
offset | The location of the cell relative to current tape position

### loop
type       | `loop`
contents   | An array of the commands making up the loop body
isBalanced | Whether execution of the loop body ends in same cell it started in

### clear
type   | `clear`
offset | The location of the cell relative to current tape position