fix: changed loop variable from const to let

[matiasbontempo]

When trying to use the library, there's an error saying the following:

25 |     for (const i = 1; i <= UNIVERSE_LEN; i++) {
                                              ^
error: This assignment will throw because "i" is a constant
    at {BASE_PATH}\node_modules\dmx\drivers\bbdmx.js:25:42

This PR changes the i type from const to let to allow the for loop to re-assign the variable.

[wiedi]

thanks!