Add Monoid for Add Point (#845)

[Boarders]

Adds Monoid for Pointed and also adds an idempotent proof for <∣>.

Note: I don't know the standard library very well (nor much module-fu) so please feel free to make suggestions for improvements.

[MatthewDaggitt]

Thank you for the great first PR, we really appreciate it! Just a heads-up that this isn't the easiest low-hanging-fruit on the tree, so it might require a couple of review iterations 😅

I've started off with the most important points and we can go from there.

[Boarders]

Have another draft of this attempting to address your points so far @MatthewDaggitt .

[MatthewDaggitt]

Thanks, here are a few more!

[Boarders]

Have another draft whenever you have the time @MatthewDaggitt

[MatthewDaggitt]

Thanks. Here's the final(?) batch.

You will also need to an entry in the CHANGELOG.md file the top level describing the changes. One entry in the new modules section, and one entry in the minor changes section.

[Boarders]

Updated with the suggested improvements.

[MatthewDaggitt]

Thanks! Apologies I've found a few more small points, but then it really is finished, promise!

[Boarders]

Life got in the way of this, will make these changes this week!

[MatthewDaggitt]

@Boarders any prospect of you finding the time to make the last tweaks so I can merge this in?

[Boarders]

Ah apologies, this completely slipped off my radar. Should be able to get these changes to you today!

[Boarders]

I made these changes but let me know if you don't like the style of naming I introduced and I'm happy to change it or anything else I overlooked. Thank you for such through reviewing and apologies for the delay.

[MatthewDaggitt]

Looks great! As soon as the tests pass I'll merge it in 👍 Thanks for the PR!