Add PyPI install instructions

Author: JosephRedfern

.github/workflows/test.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.11"]
+        python-version: ["3.11", "3.12"]
 
     steps:
     - uses: actions/checkout@v4

README.md

@@ -4,6 +4,20 @@ Docker images from within the host operating system without incurring the overhe
 
 This tool relies on some potentially unstable docker implementation details, and may break in future Docker versions!
 
+## Installation
+
+This tool can be installed from PyPI using:
+
+```bash
+pip install docker-mounter
+```
+
+Alternatively, the tool can be installed from source using:
+
+```bash
+poetry install
+```
+
 ## Compatibility
 Due to use of overlay2, tool is only compatible with Linux 3.19+.