Add a banner to mention the data corruption bug

[rasky]

Until #22 is fixed, this library is using zstd in a way that can cause data corruption, as confirmed by zstd maintainer himself. I think this is critical enough that should be mentioned at the top of README and the Go community should be alerted until the bug is fixed.

[arl]

IMHO this should be addressed.

We were using this library in production and had to switch to another one because of that.

We only noticed something was off because the sizes of the compressed files were, in some cases, up to 4x bigger than normal. Fortunately we didn't have data corruption.

The README indicates it is stable

[Viq111]

Hi @rasky & @arl,

Sorry I was out last week so getting to review this now.
Indeed, this is a pretty annoying bug that I have been trying to get a consistent reproducible test case for.
As mentioned in #22 (comment), switching to using the ZSTD_compressStream zstd interface will likely fix the issue though I would really like to be able to consistently reproduce first to make 100% we fix both cases (#22 is easy to test #39 is harder)

@rasky Would you have a set of settings where you are able to reproduce the corruption bug consistently ?

Also if anyone is interested in contributing, I only have my free time to contribute to that repository so it's a bit harder for me to undertake big API changes

Sorry again for the wasted time this has caused to anyone
(Going to close that PR in favor of #77 but feel free to continue discussing here)