feat: Adjustable config and sensible defaults

[csshugs]

Currently, the user has to completely override the $FLUIDMS-CONFIG map in order to adjust individual attributes of the Sass map. The current default of $FLUIDMS-CONFIG is this:

$FLUIDMS-CONFIG: (
    min-font-size: 16px,
    max-font-size: 24px,
    min-viewport: 480px,
    max-viewport: 1280px,
    ratio: 1.1,
    768px: (
        ratio: 1.2,
    ),
    1280px: (
        ratio: 1.3,
    ),
    scales: (
        6,
        5,
        4,
        3,
        2,
        1,
        0,
        -1,
        -2,
        -3,
    ),
) !default;

Let’s say, the user only wants to adjust the min-font-size to 18px. What they need to do is to override the map with this:

$FLUIDMS-CONFIG: (
    min-font-size: 18px,
    max-font-size: 24px,
    min-viewport: 480px,
    max-viewport: 1280px,
    ratio: 1.1,
    768px: (
        ratio: 1.2,
    ),
    1280px: (
        ratio: 1.3,
    ),
    scales: (
        6,
        5,
        4,
        3,
        2,
        1,
        0,
        -1,
        -2,
        -3,
    ),
) !default;

It would be way easier for the user to just adjust the map entry they actually want to change from the default without the need to manually copy all the contents from the original Sass map:

$FLUIDMS-CONFIG: (
    min-font-size: 18px
) !default;

If we do this, we need to overthink our current defaults of the $FLUIDMS-CONFIG Sass map, as we couldn’t remove e.g. custom breakpoint ratios. The following seems like a more sensible default config, as in it is usable right off the bat in any project with only slight adjustments (i.e. less opinionated):

$FLUIDMS-CONFIG: (
    min-font-size: 15px,
    max-font-size: 20px,
    min-viewport: 480px,
    max-viewport: 1280px,
    ratio: 1.15,
    scales: (
        6,
        5,
        4,
        3,
        2,
        1,
        0,
        -1,
        -2,
    ),
) !default;

[csshugs]

#29 is merged.