perf: avoid per-chunk byte[] copy in CryptifyClient.StoreChunkAsync (#30)

Use the ByteArrayContent(buffer, offset, count) overload to slice the
source array without copying, instead of allocating a fresh byte[] per
chunk and BlockCopy'ing into it.

For a 100 MB upload at the 1 MB chunk size this avoids 100 redundant
1 MB allocations on top of the original buffer.

Closes #27

Co-authored-by: dobby-yivi-agent[bot] <275734547+dobby-yivi-agent[bot]@users.noreply.github.com>

Author: dobby-coder[bot]

src/Api/CryptifyClient.cs

@@ -89,12 +89,9 @@ public async Task<string> UploadAsync(
     private async Task<string> StoreChunkAsync(
         string uuid, string token, byte[] data, int offset, int end, CancellationToken ct)
     {
-        var chunk = new byte[end - offset];
-        Buffer.BlockCopy(data, offset, chunk, 0, chunk.Length);
-
         var request = new HttpRequestMessage(HttpMethod.Put, $"{_cryptifyUrl}/fileupload/{uuid}")
         {
-            Content = new ByteArrayContent(chunk)
+            Content = new ByteArrayContent(data, offset, end - offset)
         };
         request.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
         request.Content.Headers.Add("Content-Range", $"bytes {offset}-{end}/*");