Add Dowe language and icon extensions

[varbdev]

Summary

• Add the Dowe language extension from https://github.com/usedowe/dowe-zed.
• Add the separate dowe-icons extension from the icons subdirectory.
• Register both extensions at version 0.1.0 using HTTPS submodule URLs.

Why

This makes Dowe discoverable and installable through Zed's official extension registry. The language extension uses the public v0.1.0 release for managed language-server assets, and the icon theme is kept as a separate extension as required by the current registry structure.

Validation

• Ran pnpm sort-extensions.
• Ran the Dowe extension grammar tests and extension checks.
• Verified the public usedowe/dowe-zed release contains macOS, Linux, and Windows language-server assets.

[cla-bot]

We require contributors to sign our Contributor License Agreement, and we don't have @varbdev on file. You can sign our CLA at https://zed.dev/cla. Once you've signed, post a comment here that says '@cla-bot check'.

[cla-bot]

We require contributors to sign our Contributor License Agreement, and we don't have @varbdev on file. You can sign our CLA at https://zed.dev/cla. Once you've signed, post a comment here that says '@cla-bot check'.

[varbdev]

@cla-bot check

[cla-bot]

The cla-bot has been summoned, and re-checked this pull request!

[MrSubidubi]

Please remove the icon theme here, I see no advantage in having that given that it just ships a singular icon.

As for the other extension, overall looks good, will take another look once that is done

[varbdev]

MrSubidubi

Done, thanks