numbers => [zéro, un, deux, trois, quatre, cinq, six, sept, huit, neuf,
    dix, onze, douze, treize, quatorze, quinze, seize,
    20 => vingt, 30 => trente, 40 => quarante, 50 => cinquante, 60 => soixante,
    70 => soixante-dix,     // 60 + 10
    71 => soixante et onze, // 60 + 11
    80 => quatre-vingts,    //  4 * 20
    100 => cent
]
rules => [
    21,31,41,51,61 => {ten} et un,
    17-69 => {ten}-{digit},
    72-79 => soixante-({num}-60),      //     60 + 12..19
    81-99 => quatre-vingt-({num}-80),  // 4 * 20 +  1..19
    200,300,400,500,600,700,800,900 => {digit} cents
]
exponents => [mille, million, milliard, trillion]
separator => ' '
replace => [un mille => mille]