minor mod: Using empty (U+0020) instead of brailEmpty

[canta2899]

I've been using logo-ls for a while and in some cases white-spaces between icons and file names were rendered as follows.

I checked out the implementation and noticed that the U+2800 Braille pattern has been used since commit 1a227b5 as a space character, except for when the -i flag is risen. However, I found out that U+2800 does not act as a proper space in the Unicode standard, according to this unicode-explorer page.

I replaced U+2800 with U+0020, the standard space character. Then, the output was properly rendered on every terminal.

I hope this PR might be helpful and thank you for making logo-ls!