Add link to iron-io/lambda

[unixorn]

Description

Add link to to iron-io/lambda

Type of changes

• A link to an external resource like a blog post or video
• Add/remove a lambda function
• Add/remove a framework
• Text cleanups/typo fixes

Checklist:

• I have confirmed that the link(s) in my PR are valid.
• My entries are single lines (unless they're a framework) and are in the appropriate (functions, frameworks, resources) section.
• My entries have been added in alphabetical order in their section.
• I have read the CONTRIBUTING document.
• All new and existing tests passed.
• I have stripped leading aws- or aws-lambda- from the link name. This makes it easier to find things by name since there aren't big clusters in the A sections of the lists
• This list is Apache 2.0 licensed, and I agree that my PR is subject to that license.