Fix typo (#541)

* Fix typo

* Update README.md

Author: akirataguchi115

apps/vanilla-app/README.md

@@ -16,7 +16,7 @@ To run this example, execute:
 $ npm start
 ```
 
-Visit http://localhost:8080 to check avaiable examples.
+Visit http://localhost:8080 to check available examples.
 
 ## Examples
 
@@ -25,5 +25,5 @@ Visit http://localhost:8080 to check avaiable examples.
 | transcode.html | Transcoding example |
 | transcode-mt.html | Transcoding example using multi-thread |
 | transcode.esm.html | Transcoding example using module |
-| trim.html | Video trimming exmple |
-| concatDemuxer.html | Video concat exmple |
+| trim.html | Video trimming example |
+| concatDemuxer.html | Video concat example |