Add "Transform message format" tutorial

[dulajdilshan]

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[dulajdilshan]

Let's review the main.bal implementation and test.bal first, and then add the README.md

[MaryamZi]

As we discussed, this test is kinda redundant, right? Since we have testInvalidHospital.

[MaryamZi]

Let's revisit the rest based on this. Can do separately.

Approved by mistake.