Add references in README.md and .gitignore file

Correct gitignore file

.gitignore

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+**/*-backups

README.md

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+
+
+### References
+
+- [Sam vs Sound](https://samvssound.com/)
+- [Sam vs Sound: Atari Punk Console](http://samvssound.com/projects/synthesizers/atari-punk-console/)
+- [Atari Punk Console Improved](https://samvssound.com/tag/stepped-tone-generator/)
+- [Music from Outer Space](http://musicfromouterspace.com/index.php?MAINTAB=SYNTHDIY&PROJARG=YOURANALOGSYNTH/page2.php&VPW=1354&VPH=556)
+- [Music From Outer Space: Projects](http://musicfromouterspace.com/index.php?MAINTAB=SYNTHDIY&PROJARG=ALIENSCREAMER%2FALIENSCREAMER.php&CATPARTNO=ALIENSCREAMERPCB)