feat: Download Diagram as SVG or PNG + Download and Upload Diagram Code

[sebastian-sommerfeld-io]

This pull request introduces several new features to enhance the usability of our diagram editor. These features provide users with more flexibility in how they interact with their diagram code and the resulting visualizations.

• https://github.com/sommerfeld-io/krokidile/issues/47
  • Users can now download the raw diagram code directly from the editor. This feature allows users to easily save and share their work outside of the application. The download is triggered by clicking the 'Code' button in the actions menu.
• https://github.com/sommerfeld-io/krokidile/issues/24
  • In addition to viewing diagrams within the application, users can now export diagrams as SVG or PNG files. This provides more flexibility for users who want to use their diagrams in other applications or contexts. The export is initiated by clicking either the 'SVG' or 'PNG' button in the actions menu.

These features were implemented with careful consideration of the existing user interface and workflows. They are expected to provide significant value to our users, making it easier for them to create, share, and reuse diagrams.

[sebastian-sommerfeld-io]

:tada: This PR is included in version 0.6.0 :tada:

The release is available on GitHub release

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