docs: update README for conventional-changelog-conventionalcommits wi…

…th example (#632)

packages/conventional-changelog-conventionalcommits/README.md

@@ -6,6 +6,40 @@ A concrete implementation of the specification described at
 [conventionalcommits.org](https://conventionalcommits.org/) for automated
 CHANGELOG generation and version management.
 
+
+## Indirect Usage (as preset)
+
+Use the [Conventional Changelog CLI Quick Start](https://github.com/conventional-changelog/conventional-changelog/tree/master/packages/conventional-changelog-cli#quick-start) with the `-p conventionalcommits` option.
+
+## Direct Usage (as a base preset so you can customize it)
+
+If you want to use this package directly and pass options, you can use the [Conventional Changelog CLI Quick Start](https://github.com/conventional-changelog/conventional-changelog/tree/master/packages/conventional-changelog-cli#quick-start) and with the `--config` or `-n` parameter, pass a js config that looks like this
+```
+'use strict'
+const config = require('conventional-changelog-conventionalcommits')
+
+module.exports = config({
+    "issuePrefixes": ["TEST-"],
+    "issueUrlFormat": "myBugTracker.com/{prefix}{id}"
+})
+```
+
+or json config like that:
+```
+{
+    "options": {
+        "preset": {
+            "name": "conventionalchangelog",
+            "issuePrefixes": ["TEST-"],
+            "issueUrlFormat": "myBugTracker.com/{prefix}{id}"
+        }
+    }
+}
+```
+This last json config way passes the `preset` object to the `conventional-changelog-preset-loader` package, that in turn, passes this same `preset` object as the config for the `conventional-changelog-conventionalcommits`.
+
+
+
 See [conventional-changelog-config-spec](https://github.com/conventional-changelog/conventional-changelog-config-spec) for available
 configuration options.