update license and readme

LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2024 Permafrost Software <oss@permafrost.dev>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

@@ -2,17 +2,20 @@
 
 ---
 
+check if a project has any changed source files
 
+## Usage
 
-check if a project has any changed source files
+- `project-indexer index <path>` - index a project's source files and write the index to a file
+- `project-indexer check <path>` - check if a project has any changed source files, must have been indexed with `index` first
+- `project-indexer has-changes <path>` - check if a project has any changed source files; exit code 0 if there are no changes, 1 if there are changes
 
 ## Setup
 
 ```bash
 go mod tidy
 ```
 
-
 ## Building the project
 
 ```bash