feat: allow to use signals to get breakpoints

[tutkli]

Previously only straight breakpoint keys could be used to get breakpoints. This change allows to use keys, signals or functions to get the breakpoints.

Usage:

private breakpoints = observeBreakpoints(breakpointsTailwind);

// Could be any type of Signal (signal, computed, input...)
public signalBreakpoint = signal<keyof typeof breakpointsTailwind>("sm")
public isSmallerOrEqual = this.breakpoints.smallerOrEqual(this.signalBreakpoint) // we use the signal without calling the value

Fixes #1