Migrate task 1.3 from Measurements to Distinguishing States kata

[moumita-halder]

Migrating task 1.3 from the Measurements workbook to Distinguishing States Kata.
This resolves a part of the Issue 1185.

• Added folder plus_minus under distinguishing_states
• Added index, placeholder, solution, and verification under plus_minus
• Updated index file under distinguishing_states to contain the exercise plus_minus

[moumita-halder]

@microsoft-github-policy-service agree

[tcNickolas]

Looks great, just a couple of small suggestions!

One note, when you're working on a kata that is not published yet, like this one, you need to add it to the list of published katas at index.json to make sure it shows up in the playground and is covered by CI builds. Here's the change I did locally to test it:

Then we remove it as the last thing before merge (I can remove that addition myself when I approve the PR, just want to mention that it needs to be removed, lest we forget to and publish the work prematurely)

Thank you!

[moumita-halder]

Thank you so much for reviewing - I was able to check in the suggested changes!
I'll make a note to include the current kata in the list of published katas in index.json, and I'll be sure to mention its removal later on

[tcNickolas]

Looks great, and I checked that it builds fine locally.
Thank you!