Document the release engineering specifics for how the IDE extension is published to marketplaces

[jwmatthews]

This task is to ensure that we document in the repo how we handle the publishing of IDE extension to both of the IDE Marketplaces.

• https://marketplace.visualstudio.com/items?itemName=konveyor.konveyor
• https://open-vsx.org/extension/Konveyor/konveyor

The VSCode Marketplace side has been automated at https://github.com/konveyor/editor-extensions/blob/main/.github/workflows/release.yml#L86

I am not sure if we've automated the open-vsx.org side yet or if the publish has been manual to date.

[jwmatthews]

#929 will handle publishing to open-vsx.org