extension-sdk: Add a shared vite config for extensions

[dschmidt]

Description

Add a shared vite config file that can be used to develop external extensions.

Related Issue

• Epic: Extension system #7930

Motivation and Context

How Has This Been Tested?

We ported

• https://github.com/dschmidt/web-app-gpx-viewer
• https://github.com/cernbox/web-extensions -> top-bar extension

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Technical debt
• Tests

Checklist:

• Code changes
• Unit tests added
• Acceptance tests added
• Documentation ticket raised:

[update-docs]

Thanks for opening this pull request! The maintainers of this repository would appreciate it if you would create a changelog item based on your changes.

[ownclouders]

Results for acceptance oC10 https://drone.owncloud.com/owncloud/web/32686/75/1
💥 The oC10IntegrationApp2 tests pipeline failed. The build has been cancelled.

[ownclouders]

Results for acceptance oC10 https://drone.owncloud.com/owncloud/web/32686/73/1
💥 The oC10IntegrationNotifications tests pipeline failed. The build has been cancelled.

[ownclouders]

Results for acceptance oC10 https://drone.owncloud.com/owncloud/web/32686/74/1
💥 The oC10IntegrationApp1 tests pipeline failed. The build has been cancelled.

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

0.0% Coverage
0.0% Duplication

[diocas]

Hi @dschmidt @kulmann , just a "small favour". I know this is not a very important PR, but it's also not that big nor changes the web code in a meaningful way..
So, do you think you could merge it today? This way I would avoid a fork to build our extensions.

[kulmann]

@dschmidt do you still want to add anything to this PR or can it be merged?

[dschmidt]

Ok to merge I guess

[diocas]

Thank you all!