Add extension to Positron

[mrmorgan17]

This is a great theme. I have recently found that the extension is not available for Positron since Positron doesn't use VS Code's Marketplace. Positron states that they use the third-party marketplace, OpenVSX. So, would it be possible for you to add the theme to the OpenVSX marketplace? You shouldn't have to make any changes to the theme itself as Positron is built on Code OSS, so VS Code extensions cane be used in Positron just as they are in VS Code. You should just be able to post the .vsix file for this theme on OpenVSX.