Use more inclusive language in documentation

[leggsimon]

Taking inspiration from @carolstran, this PR changes some occurrences of some condescending language (“simply”, “easy”, “just” etc…) from the documentation. I haven’t changed all instances and possible some changes don’t make complete sense so some input or suggestions would be nice.

[adamwathan]

Thanks! There are a few changes here that I absolutely agree are an improvement 👍🏻 However, many of them are actually changing the meaning of what's being said or replacing usage that isn't making assumptions about the reader's skills or experience, like using "just" as a synonym for "only" (stuff that's generally like "If you want to change the entire color palette, do this. If you want to change just the background colors, do this.")

Going to close this because even though the topic is important, I think the changes here are a bit too sweeping, and as the original author I'd prefer to revisit the areas that I think could use improvement myself to make sure the original intention and voice is preserved.

Thanks again ❤️