Manually Update SilverStripe Extension

[manuth]

• 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

As described in #767, the SilverStripe extension is unmaintained and hints the incorrect version number in its package.json file. Furthermore, the current .vsix file hosted on Open-VSX is broken and doesn't work properly - even causing other extensions to not getting loaded.

Therefore, changes made in this PR will:

• Check out the (at time of writing) most recent commit
• Set the (at time of writing) most recent version number in the package.json file
• Apart from that publish it normally

Merging this PR will close #767

[filiptronicek]

Long time no see, @manuth!

Thanks for this, I've tried the produced package locally, and it seems to work as expected. I'm going to merge this, and after it gets published remove the extension from the list, because it does not seem like it will get any further updates.

[manuth]

Awesome to hear from you again! 😄
tysm for taking care!