add more info about implementing your own service

docs/03_Implement_a_service.md

@@ -6,10 +6,45 @@ This Page will describe how you can implement and add your own. Please make sure
 and the [Concept of LinkHandler](https://teamnewpipe.github.io/documentation/02_Concept_of_LinkHandler/)
 before implementing your own Service.
 
-- [ServiceList](https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/ServiceList.html)
+### Allowed Libraries
+
+The NewPipe Extractor already comes a long with a lot of usable tools and external libraries that should make extracting easy.
+For some specific (tiny) tasks regex is allowed. Here you can take a look at the
+[Parser](https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/utils/Parser.html),
+which will give you a little help with that. __Use Regex with care!!!__ Avoid it as often as possible. It's better to
+ask us to introduce a new library than start using regex to often.
+
+- Html/XML Parsing: [jsoup](https://jsoup.org/apidocs/overview-summary.html)
+- JSON Parsiong: [nanojson](https://github.com/mmastrac/nanojson#parser-example)
+- JavaScript Parsing/Execution: [Mozilla Rhino](https://developer.mozilla.org/en-US/docs/Mozilla/Projects/Rhino/Documentation)
+- Link dectection in strings: [AutoLink](https://github.com/robinst/autolink-java)
+
+If you need to introduce new libraries please tell us before you do it.
+
+### Head of Service
+
+First of all if you want to create a new service you should create a new package below `org.schabi.newpipe.services`
+, with the name of your service as package name. Here you must put an implementation of these two classes:
+
 - [StreamingService](https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/StreamingService.html)
 - [ServiceInfo](https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/StreamingService.ServiceInfo.html)
 
+[StreamingService](https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/StreamingService.html)
+is a factory class that will return objects of all important parts of your service.
+Every extractor Kisok, Info type you add, and which should be part of your implementation must be instantiated using an
+instance of this class.
+
+[ServiceInfo](https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/StreamingService.ServiceInfo.html)
+will return some meta information about your service. Such as the name, the capabilities, and your name as well as your 
+email address for further notice and maintenance issues. Remember, after extending this class you need to return an
+instance of it by through your implementation of
+[`StreamingService.getServiceInfo()`](https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/StreamingService.html#getServiceInfo--).
+
+When these two classes are extended by you, you need to add them to the
+[ServiceList](https://github.com/TeamNewPipe/NewPipeExtractor/blob/49c2eb51859a58e4bb5ead2d9d0771408f7d59d6/extractor/src/main/java/org/schabi/newpipe/extractor/ServiceList.java#L23)
+of NewPipe. This way the will become an official part of the NewPipe Extractor.
+Every service has an ID, which will be set when this list gets created. You set this Id by entering it in the constructor.
+So when adding your service just give it the ID of the previously last service in the list incremented by one.
 
 ### Search
 - [SearchExtractor](https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/search/SearchExtractor.html)