typo in README

[codecov[bot]]

Codecov Report

Base: 100.00% // Head: 100.00% // No change to project coverage :thumbsup:

Coverage data is based on head (6b495f9) compared to base (8d790ff). Patch has no changes to coverable lines.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #26 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 5 5 Lines 358 358 ========================================= Hits 358 358 ``` Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaImages). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaImages)

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[RexWzh]

Thanks for the correction @yakir12.

There may be some other typos in the code. Another typo I just found:

# line 81: and => can
QR Codes and be encoded with four error correction levels `Low`, `Medium`, `Quartile` and `High`. 

I'll take an overall review on function docs too when available, and would appreciate it if you could help with this.