Disallow inline display maths

[rda0]

This fixes element-hq/element-web#17095 by changing the default regex for display maths to only parse display maths when it starts and ends on a new line.

I believe this is acceptable since display maths will be rendered using the full page width anyway.

The default behavior in config.json can now be reproduced as follows:

    "latex_maths_delims": {
        "inline": {
            "left": "\\(",
            "right": "\\)",
            "pattern": {
                "latex": "(^|[^\\\\])\\\\\\((?!\\\\\\))(.*?)\\\\\\)",
                "tex": "(^|\\s|[.,!?:;])(?!\\\\)\\$(?!\\s)(([^$\\n]|\\\\\\$)*([^\\\\\\s\\$]|\\\\\\$)(?:\\\\\\$)?)\\$"
            }
        },
        "display": {
            "left": "\\[",
            "right": "\\]",
            "pattern": {
                "latex": "(^)\\\\\\[(?!\\\\\\])(.*?)\\\\\\]$",
                "tex": "(^)\\$\\$(([^$]|\\\\\\$)+?)\\$\\$$"
            }
        }
    },