Add explicit node outline color to Container Images mermaid

[CBroz1]

Edit needed here

Example - color scheme in last 2 lines below. Works with both dark and light modes of current styling

flowchart LR
  py_interp  -->|DataJoint| db_server[("Database Server\n(e.g., MySQL)")]
  subgraph conda["Conda environment"]
    direction TB
    py_interp[Python Interpreter]
  end
  subgraph empty1[" "] %% Empty subgraphs prevent overlapping titles
    direction TB
    style empty1 fill:none, stroke-dasharray: 0 1
    conda
  end
  subgraph term["Terminal or Jupyter Notebook"]
    direction TB
    empty1
  end
  subgraph empty2[" "] %% Empty subgraphs prevent overlapping titles
    direction TB
    style empty2 fill:none, stroke-dasharray: 0 1
    term
  end
  subgraph ide["Integrated Development Environment"]
    direction TB
    empty2
  end
  class py_interp,conda,term,ide,db_server,DataJoint boxes;
  classDef boxes fill:#ddd, stroke:#333;

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flowchart LR
  py_interp  -->|DataJoint| db_server[("Database Server\n(e.g., MySQL)")]
  subgraph conda["Conda environment"]
    direction TB
    py_interp[Python Interpreter]
  end
  subgraph empty1[" "] %% Empty subgraphs prevent overlapping titles
    direction TB
    style empty1 fill:none, stroke-dasharray: 0 1
    conda
  end
  subgraph term["Terminal or Jupyter Notebook"]
    direction TB
    empty1
  end
  subgraph empty2[" "] %% Empty subgraphs prevent overlapping titles
    direction TB
    style empty2 fill:none, stroke-dasharray: 0 1
    term
  end
  subgraph ide["Integrated Development Environment"]
    direction TB
    empty2
  end
  class py_interp,conda,term,ide,db_server,DataJoint boxes; % add all items to boxes class
  classDef boxes fill:#ddd, stroke:#333; % define fill/stroke of boxes class