add link to the chapter 3

Author: leandromoreira

README.md

@@ -31,6 +31,7 @@ __Table of Contents__
     * [FFmpeg libav architecture](#ffmpeg-libav-architecture)
   * [Chapter 1 - timing](#chapter-1---syncing-audio-and-video)
   * [Chapter 2 - remuxing](#chapter-2---remuxing)
+  * [Chapter 3 - transcoding](#chapter-3---transcoding)
 
 # Intro
 
@@ -712,6 +713,7 @@ As you can see it has a single `mdat` atom/box, **this is place where the video
 In this chapter, we're going to create a minimalist transcoder, written in C, that can convert videos coded in H264 to H265 using **FFmpeg/libav** library specifically [libavcodec](https://ffmpeg.org/libavcodec.html), libavformat, and libavutil.
 
 ![media transcoding flow](/img/transcoding_flow.png.png)
+
 > _Just a quick recap:_ **AVFormatContext** is the abstraction for the format of the media file, aka container (ex: MKV, MP4, Webm, TS), the **AVStream** represents each type of data for a given format (ex: audio, video, subtitle, metadata), **AVPacket** is a slice of compressed data obtained from the AVStream that can be decoded by an **AVCodec** (ex: av1, h264, vp9, hevc) generating a raw data called **AVFrame**.
 
 ### Transmuxing
@@ -878,6 +880,10 @@ int encode(AVFormatContext *avfc, AVStream *dec_video_avs, AVStream *enc_video_a
 ```
 
 We converted the media stream from `h264` codec:
+
 ![h264 codec properties](/img/h264_properties.png)
+
 To the `HEVC` codec:
+
 ![hevc codec properties](/img/hevc_properties.png)
+