Fix typo in README

Author: earlephilhower

README.md

@@ -13,7 +13,7 @@ All this code is released under the GPL, and all of it is to be used at your own
 * The software I2S delta-sigma 32x oversampling DAC was my own creation, and sounds quite good if I do say so myself.
 * The AAC decode code is from the Helix project and licensed under RealNetwork's RSPL license.  For commercial use you're still going to need the usual AAC licensing from [Via Licensing](http://www.via-corp.com/us/en/licensing/aac/overview.html).  On the ESP32, AAC-SBR is supported (many webradio stations use this to reduce bandwidth even further).  The ESP8266, however, does not support it due to a lack of onboard RAM.
 * MIDI decoding comes from a highly ported [MIDITONES](https://github.com/LenShustek/miditones) combined with a massively memory-optimized [TinySoundFont](https://github.com/schellingb/TinySoundFont), see the respective source files for more information.
-* Opusis from [Xiph.org](https://xiph.org) with the Xiph license and patent described in src/{opusfile,libggg,libopus}/COPYING.
+* Opus is from [Xiph.org](https://xiph.org) with the Xiph license and patent described in src/{opusfile,libggg,libopus}/COPYING.
 
 ## Neat Things People Have Done With ESP8266Audio
 If you have a neat use for this library, [I'd love to hear about it](mailto:[email protected])!