Update docs for new build CLI

Readme.md

@@ -7,7 +7,7 @@ Detect the language of text.
 # What’s so cool about franc?
 
 1. **franc** supports more languages<sup>(†)</sup> than any other library, or Google;
-2. **franc** is easily [forked](https://github.com/wooorm/franc/blob/master/script/build-languages.js#L36) to support 300+ languages;
+2. **franc** is easily [forked](#supporting-more-or-less-languages) to support 300+ languages;
 3. **franc** is just as fast as the competition.
 
 † - If humans write in the language, on the web, and the language has more than one million speakers, **franc** detects it.
@@ -98,6 +98,15 @@ franc.all('O Brasil caiu 26 posições em', {
 
 **franc** supports 175 “languages”. For a complete list, check out [Supported-Languages.md](Supported-Languages.md).
 
+## Supporting more or less languages
+
+Supporting more or less languages is easy: fork the project and run the following:
+
+```sh
+$ npm install
+$ THRESHOLD=-1 npm run build
+```
+
 ## Benchmark
 
 On a MacBook Air, it runs 175 paragraphs 2 times per second (total: 350 op/s).