Kybra 0.7.0

[lastmjs]

We are going to wait for dfx extensions to be in an official dfx release (probably 0.21.0) before releasing Kybra 0.7.0. This should happen around mid-late May 2024.

Before this release:

• Test with release candidates and main release that version in kybra/compiler/dfx_extension/extension.json is updated automatically on release
• Update all Kybra documentation with the new dfx.json format
• update extension metadata
• Explain all breaking changes (especially that Candid files are now in a new location)
• Update dfx to the latest

This release will introduce dfx extensions and greatly simplify the dfx.json file. It will also remove .did files from all of the examples, and developers will not see these files in their version control anymore as long as the .gitignore .kybra. The .did files are now in .kybra.