Celsius to Fahrenheit converter

A simple converter from Celsius to Fahrenheit and vice versa.

Convert Fahrenheit to Celsius:

The toCelsius(f, round) function takes the Fahrenheit temperature f as
a number or as a string (if string, the string must start with a number), converts
it and rounds to the round number of decimal digits. By default it rounds to
the nearest integer.

``js
const { toCelsius } = require('celsius');

toCelsius(100); // 38
toCelsius(100, 3); // 37.778
toCelsius('105.981 degrees F', 5); // 41.10056
`

Convert Celsius to Fahrenheit:

The toFahrenheit(c, round) function takes the Celsius temperature c as
a number or as a string (if string, the string must start with a number), converts
it and rounds to the round number of decimal digits. By default it rounds to
the nearest integer.

`js
const { toFahrenheit } = require('celsius');

toFahrenheit(36); // 97
toFahrenheit(36.68, 3); // 98.024
toFahrenheit('-40.691 degrees C', 5); // -41.24380
`

Append the °F or °C automatically

Use the functions toCelsiusFmt() and toFahrenheitFmt() with the same
parameters to return a string containing the converted number and the characters
°C or °F` respectively.