add webex calling postman

[jpjpjp]

Please check that what you want to add to awesome-webex meets these Quality standards before sending pull requests. Thanks!

Have you checked the boxes below before submitting your PR:

• [x] I have added my resource in alphabetical order
• [xI know that this resource was not listed before
• [x] I have added a link to the source code repo (except for documentation, articles etc.)
• [x] I have checked my resource is properly documented
• [ ] I have added a synthetic description of my resource - not sure what this means??
• [x] I have read the Contribution guidelines and Quality standards.

[ObjectIsAdvantag]

I have added a synthetic description of my resource - not sure what this means??

@jpjpjp this is the short sentence that explains what the resource is about, no worries you've included it,

though if you have another way of spelling out this requirement, I am happy to update the contribution template.

[ObjectIsAdvantag]

hi jpjpjp, I've already added the resources 2 weeks ago, sorry not to have given you the heads up closing this PR