Minor text styling options

[jo-mueller]

@dstansby PR with your wording change suggestions from here and fixes to some more text style issues (i.e., leftover Python wording instances such as "dictionary")

[github-actions]

Automated Review URLs

• Readthedocs

[lubianat]

the reference of "which" may be ambiguous. Should the array or the objects contain the fields?

As only objects have "fields", the latter is assumed. Other suggestions:

• "MUST be an array of objects, where each object MUST contain the fields input_axes, output_axes, and transformation.

• "MUST be an array. Each element MUST be an object containing the fields input_axes, output_axes, and transformation.

Also, the JSON spec does not use "field", 4. Objects:

An object structure is represented as a pair of curly brackets
surrounding zero or more name/value pairs (or members). A name is a
string. A single colon comes after each name, separating the name
from the value. A single comma separates a value from a following
name. The names within an object SHOULD be unique.

So if we are being precise...

• "MUST be an array of objects. Each object MUST contain name/value pairs with names input_axes, output_axes, and transformation."

or

• "MUST be an array of objects. Each object MUST have members named input_axes, output_axes, and transformation."

Risking bikeshedding, yet another option is to use property and define it clearly elsewhere. That is what the JSON Schema spec does in 4.2.1:

object:
An unordered set of properties mapping a string to an instance, from the JSON "object" value

Feel free to split the field/property/member thing into a separate issue, though!