Add Lazy usage instructions to README

Author: rlaphoenix

README.md

@@ -2,11 +2,43 @@
 
 Resync Chapters by snapping them to Scene Changes.
 
-## To-do
-
-- [x] Automatically replace the chapters in the input video container.
-
-Likely lot's more.
+## Usage
+
+```
+Usage: chapsnap [OPTIONS] VIDEO [CHAPTERS]
+
+  Snap Chapters to Scene Changes.
+
+  VIDEO       The video file to snap chapters to scene changes. All video formats are
+              supported. You may alternatively provide a directory path to process
+              video files in batch.
+  [CHAPTERS]  Optional chapters file if you want to use chapters from a file
+              rather than ones already muxed with the video.
+
+Options:
+  -t, --threshold FLOAT  Threshold on Scene Change probability scores. The
+                         lower the value, the more unlikely the frame is to be
+                         a Scene Change. Range: 0.0 (Impossible) - 1.0
+                         (Definite).
+  -o, --offset FLOAT     Offset to apply to each Chapter. A negative offset
+                         may result in fewer Chapters.
+  --trim INTEGER         Remove n Chapters from the start of the Video. A
+                         negative value will remove n Chapters from the end of
+                         the Video. Timestamps will be offset respectively.
+  -nf, --no-forward      Do not try to resync Chapters forward in time.
+  -nb, --no-backward     Do not try to resync Chapters backward in time.
+  -k, --keyframes        Only sync to Scene Changes on Keyframes (I-frames).
+  -0, --zero             Force the first chapter to be at `00:00:00.000`, even
+                         after offsets and trims.
+  -c, --chain            Chain sync adjustments from one Chapter to the next.
+                         E.g., Chapter 1 had -2, so Chapter 2 will begin with
+                         an offset of -2. Chapter 2 with -2 has a change of
+                         -1, so Chapter 3 will begin with an offset of -3 and
+                         so on.
+  --overwrite            Apply new Chapters to the input video file in-place,
+                         without making a duplicate.
+  --help                 Show this message and exit.
+```
 
 ## Contributors