Auto-publish Pebble extension

[griffinli]

• I have read the note above about PRs contributing or fixing extensions
• I have tried reaching out to the extension maintainers about publishing this extension to Open VSX (if not, please create an issue in the extension's repo using this template).
• This extension has an OSI-approved OSS license (we don't accept proprietary extensions in this repository)

Description

This introduces publishing the Pebble extension for development of apps for the Pebble smartwatch.

[filiptronicek]

Hi @griffinli, thanks for the contribution!

A goal of Open VSX is to have extension maintainers publish their extensions according to the documentation[1]. The first step we recommend is to open an issue with the extension owner[2]. If the extension owner is unresponsive for some time, this repo (publish-extensions) can be used as a temporary workaround to ensure the extension is published to Open VSX.

If you need help publishing the extension, feel free to reach out.