Update README with a new "weaknesses" section and commit hash example

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

README.md

@@ -25,6 +25,10 @@ No dependencies required, everything is vanilla Python >=3.10.
 
 `python -m colorhash infile.dat -y svg -o out.svg -a md5`
 
+### Create art in the terminal using the current git commit hash
+
+`python -m colorhash "$(git rev-parse HEAD)" -a sha1`
+
 # Motivation
 
 > If you see the picture is different, the key is different.
@@ -39,6 +43,13 @@ checksum of a file from the internet. The goal of this project is to give more f
 pattern recognition so that two extremely similar hashes, maliciously crafted or not, have more
 visual depth to their distinction.
 
+## Weaknesses
+
+This is not a perfect solution for hash comparison. Similar hashes may just so happen to choose the
+same color palette, for example. Additionally, if this is appearing on a webpage, caches may
+override the most recent version of the file; this has happened with me and Chrome looking at the
+Github page for this project.
+
 # Examples
 
 See the examples directory.