For next/font/local: A string or boolean false value that sets whether an automatic fallback font should be used to reduce Cumulative Layout Shift. The possible values are 'Arial', 'Times New Roman' or false. The default is 'Arial'.
Used in next/font/google and next/font/local
Optional
Examples:
adjustFontFallback: false: for ``next/font/google`
adjustFontFallback: 'Times New Roman': for next/font/local
variable
A string value to define the CSS variable name to be used if the style is applied with the CSS variable method.
Used in next/font/google and next/font/local
Optional
Examples:
variable: '--my-font': The CSS variable --my-font is declared
declarations
An array of font face descriptor key-value pairs that define the generated @font-face further.
Used in next/font/local
Optional
Examples:
declarations: [{ prop: 'ascent-override', value: '90%' }]