Paul suggested fixes and readme clean-up

[ggailey777]

Purpose

Remove Postman reference (required by MS security) and link to the new HTTP test tool section in core docs.

Does this introduce a breaking change?

[ ] Yes
[X] No

Pull Request Type

What kind of change does this Pull Request introduce?

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[X] Documentation content changes
[ ] Other... Please describe:

How to Test

• Get the code

git clone [repo-address]
cd [repo-name]
git checkout [branch-name]
npm install

• Test the code

What to Check

Verify that the following are valid

• ...

Other Information

[paulyuk]

Just a few comments to set (and forget) the working path which is actually /src/functions (where host.json lives) unless you're hitting F5 in VS or doing azd commands (where azure.yml lives)