Attempt to increase heap size to prevent error

[cwolf10]

Description

Adds an env var to the step that is currently failing which will hopefully allow this step to succeed. Per this comment, this update should resolve the issue: actions/runner-images#70 (comment)

Motivation and Context

Current github actions deployment is failing due to running out of heap space: https://github.com/GSA/sam-design-system/actions/runs/4025410379

Type of Change (Select One and Apply Github Label)

• Bug fix (non-breaking change which fixes an issue) -> Apply bugfix label
• New feature (non-breaking change which adds functionality) -> Apply enhancement label
• Breaking change (fix or feature that would cause existing functionality to change) -> Apply breaking label

Screenshots (if appropriate):

Which browsers have you tested?

• Internet Explorer 11
• Edge
• Chrome
• Firefox
• Safari

Checklist:

• I have read the (https://github.comv/GSA/sam-ui-elements/blob/CONTRIBUTING.md)[CONTRIBUTING.md] document.
• My code passes the automated linter.
• This code has been reviewed by another team member and passes the reviewer checklist found in (https://github.comv/GSA/sam-ui-elements/blob/CONTRIBUTING.md)[CONTRIBUTING.md]
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.
• My code is 508 compliant as tested by AMP and JAWS
• Any dependent changes have been merged and published in downstream modules