README: Mermaid flow diagram

[kaedonkers]

GitHub now natively supports Mermaid flow diagrams in rendered Markdown files (https://github.blog/2022-02-14-include-diagrams-markdown-files-mermaid/).

We have a flow diagram in this project, so this issue is to capture code and thinking about including an interactive flow diagram in the repo README.

[kaedonkers]

Best example I came up with was this, which isn't very satisfying:

flowchart LR
    A[Data Collection & Processing]
    B[Correlation Threshold]
    C[Random Forest]
    D[Bayesian Network]
    E[Dynamics Visualisations]
    F[Linear Regression]

    subgraph _
        direction LR
        A --> B --> C --> D --> E --> F
    end

    H[Historical Climate Indices]
    I[Global Meteorological Reanalysis]
    J[Regional Temperature Reanalysis]
    K[Chronological & Causal Rules]
    L[Global Meteorological Analysis]
    M[Regional Temperature Forecast]

    subgraph __
        direction LR
        H --> A
        I --> A
        J --> B
        J --> C
        K --> D
        L --> E
        F --> M
    end

flowchart LR
    A[Data Collection & Processing]
    B[Correlation Threshold]
    C[Random Forest]
    D[Bayesian Network]
    E[Dynamics Visualisations]
    F[Linear Regression]

    subgraph _
        direction LR
        A --> B --> C --> D --> E --> F
    end

    H[Historical Climate Indices]
    I[Global Meteorological Reanalysis]
    J[Regional Temperature Reanalysis]
    K[Chronological & Causal Rules]
    L[Global Meteorological Analysis]
    M[Regional Temperature Forecast]

    subgraph __
        direction LR
        H --> A
        I --> A
        J --> B
        J --> C
        K --> D
        L --> E
        F --> M
    end