added contributing info

README.md

@@ -7,6 +7,8 @@
 5. [About the Audio](#download)
 6. [About the Lyrics](#lyrics)
 
+I am happy about every pull request. To contribute look [here](contribute.md).
+
 ![](https://github.com/HeIIow2/music-downloader/blob/master/assets/logo_cropped.jpg?raw=true)
 
 ## Installation

contribute.md

@@ -0,0 +1,13 @@
+# How to contribute
+
+I am always happy about pull requests.  
+If you wanna contribute, this is for you. Some options will follow:
+
+## Add an audio/metadata source
+
+The audio and Metadata Sources all inherint the class `Page` in [abstract.py](src/music_kraken/pages/abstract.py)
+
+You can create a subclass of this class for for example youtube or musify or whatever.  
+I documented the function it should have in the docstrings of [abstract.py](src/music_kraken/pages/abstract.py). If you are unsure about how it works, look at either the doccumentation *(will get more detailed soon)* or an [example](src/music_kraken/pages/encyclopaedia_metallum.py). For trying you're class you can make a skript simmilar to [this one](src/metal_archives.py). Make sure it is in the same directory though.
+
+> Read the part of the documentation, I already have written. 

src/music_kraken/pages/youtube.py

@@ -0,0 +1,46 @@
+from typing import List
+import requests
+from bs4 import BeautifulSoup
+import pycountry
+
+from ..utils.shared import (
+    ENCYCLOPAEDIA_METALLUM_LOGGER as LOGGER
+)
+
+from .abstract import Page
+from ..database import (
+    MusicObject,
+    Artist,
+    Source,
+    SourcePages,
+    Song,
+    Album,
+    ID3Timestamp,
+    FormattedText
+)
+from ..utils import (
+    string_processing
+)
+
+INVIDIOUS_INSTANCE = "https://yewtu.be/feed/popular"
+
+class Youtube(Page):
+    """
+    The youtube downloader should use https://invidious.io/
+    to make the request.
+    They are an alternative frontend.
+
+    To find an artist filter for chanel and search for
+    `{artist.name} - Topic`
+    and then ofc check for viable results.
+
+    Ofc you can also implement searching songs by isrc.
+
+    NOTE: I didn't look at the invidious api yet. If it sucks,
+    feel free to use projects like youtube-dl.
+    But don't implement you're own youtube client.
+    I don't wanna maintain that shit. 
+    """
+    API_SESSION: requests.Session = requests.Session()
+
+    SOURCE_TYPE = SourcePages.YOUTUBE