Helper functions for data management keys

[jmcdo29]

It would be nice if we had a helper function to generate the keys for the data management. Ran into a small bug earlier because I forgot a { when working with a template literal (something along the lines of

`$S${someVariable}}`

when it should have had one more { before the second $. To alleviate this now I've made a helper function to generate the keys for me

export const getStashKey = (key: string) => `$S{${key}}`

And can do the same for the data maps and function.

While we're at it, could we also export some constants for @OVERRIDES@ and @DATA:TEMPLATE@? I've made some in my local code, but figure it could be nice to have it provided by the library as well

[ASaiAnudeep]

Yes, makes sense.

Original idea was to create a plugin in vs-code for highlighting the special syntax from pactum. For a quick fix, as you suggested we can include some helper methods for avoiding typos in data management.