add NumberToString conversion map

.gitignore

@@ -2,3 +2,4 @@
 node_modules
 lib
 dev
+/.idea/

src/index.ts

@@ -151,6 +151,8 @@ export type Max<N1 extends Nat, N2 extends Nat> = If<Lte<N1, N2>, N2, N1>
  */
 export type NumberToNat = TupleToObject<[_0, _1, _2, _3, _4, _5, _6, _7, _8, _9, _10]>
 
+export type NumberToString = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '10']
+
 /** max Nat = _10 */
 export type NatToNumber<N extends Nat> = If<
   NatEq<N, _0>,

typings-checker/index.ts

@@ -92,3 +92,8 @@ const e4: E1 = { a: 'foo', b: true, c: 1 }
 
 type TTO = t.TupleToObject<[number, string]>
 const tto1: TTO = { 0: 1, 1: 'foo' }
+
+type FIVE = t.NumberToString[5]
+const n2s1: FIVE = '5'
+// $ExpectError Type '"6"' is not assignable to type '"5"'
+const n2s2: FIVE = '6'