Implement functions to encrypt and decrypt a message using the [straddling checkerboard](https://en.wikipedia.org/wiki/Straddling_checkerboard) method. The functions will take a string and an array as parameters. The array has 3 strings representing the 3 rows of the checkerboard. The output will be a series of decimal digits. Numbers should be encrypted by inserting the escape character before each digit, then including the digit unencrypted. This should be reversed for decryption.
# --hints--
`straddle` should be a function.
```js
assert(typeof straddle == 'function');
```
`straddle("One night-it was on the twentieth of March, 1888-I was returning.",["ESTONIA R", "BCDFGHJKLM", "PQUVWXYZ./"])` should return a string.
```js
assert(
typeof straddle(
'One night-it was on the twentieth of March, 1888-I was returning.',
['ESTONIA R', 'BCDFGHJKLM', 'PQUVWXYZ./']
) == 'string'
);
```
`straddle("One night-it was on the twentieth of March, 1888-I was returning.",["ESTONIA R", "BCDFGHJKLM", "PQUVWXYZ./"])` should return `"34045747525284613427502840425027537379697175891898898898584619028294547488"`.
```js
assert.equal(
straddle(
'One night-it was on the twentieth of March, 1888-I was returning.',
`straddle("One night-it was on the twentieth of March, 1888-I was returning",["HOL MES RT", "ABCDFGIJKN", "PQUVWXYZ./"])` should return `"139539363509369743061399059745399365901344308320791798798798367430685972839363935"`.
```js
assert.equal(
straddle('One night-it was on the twentieth of March, 1888-I was returning', [
`straddle("Thecheckerboardcakerecipespecifies3largeeggsand2.25cupsofflour.",["ET AON RIS", "BCDFGHJKLM", "PQ/UVWXYZ."])` should return `"125021250212707204372221327070218600960021823809623283724002424935226226962262521636094232328463769"`.
`unstraddle("34045747525284613427502840425027537379697175891898898898584619028294547488",["ESTONIA R", "BCDFGHJKLM", "PQUVWXYZ./"])` should return a string.
`unstraddle("139539363509369743061399059745399365901344308320791798798798367430685972839363935",["HOL MES RT", "ABCDFGIJKN", "PQUVWXYZ./"])` should return `"ONENIGHTITWASONTHETWENTIETHOFMARCH1888IWASRETURNING"`.
`unstraddle("125021250212707204372221327070218600960021823809623283724002424935226226962262521636094232328463769",["ET AON RIS", "BCDFGHJKLM", "PQ/UVWXYZ."])` should return `"THECHECKERBOARDCAKERECIPESPECIFIES3LARGEEGGSAND2.25CUPSOFFLOUR."`.