render_mermaid: generate mermaid code from app code analysis
In basf/reactflush: Shiny Code Reactivity Visualizer

generate mermaid code from app code analysis

1 2	render_mermaid(app, network, focus, focus_field = c("name", "id", "type"))

`app`	`data.frame` containing all code blocks, inputs and reactives
`network`	`data.frame` containing all reactive dependencies
`focus`	`string` reactive node to focus on, all it's dependencies on blocks which depend on it will be shown
`focus_field`	`enum` what the type of the focus argument is: `name`: assigned name of reactive block (`(output$)<name> <- reactive/render*`) `id`: assigned id by `parse_code_blocks` `type`: type of block (reactive, observeEvent, ...)