Base64 decode error points at the wrong character when the input has spaces or line breaks #310

Decode SGVs bG8! in the Base64 tool. The error says the illegal character "!" is at position 7, but in what you typed it's the 9th character. base64ToBytes (lib/base64-utils.ts, line 38) strips all whitespace first (line 41) and reports the index in the stripped string, counted from 0 (lines 48 to 53). With pasted multi-line Base64 the number is even further off.

What to do

• Report where the character is in the original input, counted from 1. For input with line breaks, line and column is even clearer.

Where to look

• lib/base64-utils.ts: base64ToBytes (lines 38 to 60)
• lib/__tests__/base64-utils.test.ts

Acceptance criteria

• SGVs bG8! reports position 9
• An illegal character on the second line of multi-line input is reported where it really is
• Tests that fail on the current code
• npm run lint, npm run test and npm run build pass

Want to work on this? Comment below and I'll assign it to you. Please take one issue at a time, branch off develop, and open your PR against develop with Closes #310 in the description.