github/workflows: add PR size labeler

[raiden00pl]

Summary

Add workflow that assigns labels based on the PR's size.
Based on https://github.com/marketplace/actions/pull-request-size-labeler

This is an external action, but it's used also in Apache Mynewt-nimble project, so I think it's ok: https://github.com/apache/mynewt-nimble/blob/master/.github/workflows/labeler.yml

This allows easy filtering of PR by the size of changes

Impact

Each PR will have a label assigned depending on its size:
xs_label: 'Size: XS', max size = 10
s_label: 'Size: S', max size = 100
m_label: 'Size: M', max size = 500
l_label: 'Size: L', max size = 1000
xl_label: 'Size: XL', > 1000

Testing

tested on my private nuttx repo here https://github.com/raiden00pl/nuttx/pulls

[nuttxpr]

[Experimental Bot, please feedback here]

I need the content of the actual Pull Request (PR) to assess if it meets the NuttX requirements. Please provide the following:

• Link to the PR: This is the most helpful. I can directly review the PR content on GitHub.
• PR Description: If you can't share the link, copy and paste the full PR description.

With this information, I can compare it to the requirements and give you a concise answer.

[jerpelea]

@raiden00pl

please add

• SPDX-License-Identifier: Apache-2.0

in front of the Apache license

Thanks