feat(commands): add release script customizability (#12)

README.md

@@ -39,3 +39,26 @@ You can create an `.rczrc`, `.rczrc.json` or `rcz.config.json` file in your root
   "autoSignReleases": true
 }
 ```
+
+You are also able to create an onRelease event file, that is going to run before creation of a git tag and a release commit, when `rcz release` is run. The file is to be named `.rczrc.onrelease.js`. A sample can be seen below.
+
+```js
+const fs = require("fs"); // Require fileSystem
+
+const packageFile = fs.readFileSync("./package.json").toString(); // Get package.json contents from the current working directory
+const newPackageFile = packageFile.replace(
+  /"version": "[0-9]+.[0-9]+.[0-9]+"/,
+  `"version": "${__NEW_VERSION__}"`
+); // Use RegExp to replace package.json version
+
+fs.writeFileSync("./package.json", newPackageFile); // Write to package.json file its new content
+
+const indexFile = fs.readFileSync("./src/index.ts").toString(); // Get index.ts file from source code directory
+const newIndexFile = indexFile.replace(/version\("[0-9]+\.[0-9]+\.[0-9]+"\)/); // Replace class function call content with the new version
+
+fs.writeFileSync("./src/index.ts", newIndexFile); // Write to source code index file
+```
+
+In your onRelease file you are provided with `__NEW_VERSION__` constant string which is the new version submitted in `rcz release` and `__IS_SIGNED__` constant which is a boolean telling whether the release (it's commit and tag) is going to be signed.
+
+Bear in mind, **this script is going to be executed through `eval()` with no sanitation**, be careful with whatever you write.