Add code editor to properties panel entries other than FEEL

[barmac]

Problem you would like to solve

Currently, only FEEL entries in the properties panel contain a code editor with line numbers, syntax highlighting etc.
Even though "Example output" takes a JSON, there's no code assistance for that entry. We only perform validation.

Proposed solution

• Add a code editor entry, e.g. as a JSON entry (or more if necessary).

Notes on Implementation

• Non FEEL fields can already be tagged via element templates, through the language field (Improve representation of non FEEL languages bpmn-io/bpmn-js-properties-panel#858)
• We'd want to give implementors the ability to provide custom editors for specific fields, i.e. GraphQL, JSON, ... (Fully support Text#language bpmn-io/bpmn-js-properties-panel#872)

Alternatives considered

Do nothing.

Additional context

Reported by @falko via https://camunda.slack.com/archives/C0693F1NFK5/p1730978476288409?thread_ts=1730977038.364429&cid=C0693F1NFK5

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Related to bpmn-io/bpmn-js-properties-panel#858, bpmn-io/bpmn-js-properties-panel#872.

[jarekdanielak]

As it was already tagged good first issue, I'll move it to backlog.

[nikku]

I've added additional context on prior investments to issue. Specifically we supported language via element templates via bpmn-io/bpmn-js-properties-panel#858. Full support via pluggable editors (i.e. for GraphQL, JSON) is still pending via bpmn-io/bpmn-js-properties-panel#872.

[nikku]

Related to my prior talk on language tooling.