[doc] Fix links in main tutorial doc

Author: isinaltinkaya

doc/tutorial.MD

@@ -1,8 +1,8 @@
 # vcfgl - Tutorials
 
-<li><a href="https://github.com/isinaltinkaya/vcfgl/doc/install.MD">Installation</a></li>
-<li><a href="https://github.com/isinaltinkaya/vcfgl/doc/depth.MD">Simulating read depths</a></li>
-<li><a href="https://github.com/isinaltinkaya/vcfgl/doc/error_qs.MD">Simulating quality score errors</a></li>
-<li><a href="https://github.com/isinaltinkaya/vcfgl/doc/with_msprime.MD">Using vcfgl with msprime</a></li>
-<li><a href="https://github.com/isinaltinkaya/vcfgl/doc/with_stdpopsim.MD">Using vcfgl with stdpopsim</a></li>
-<li><a href="https://github.com/isinaltinkaya/vcfgl/doc/with_SLiM.MD">Using vcfgl with SLiM</a></li>
+<li><a href="https://github.com/isinaltinkaya/vcfgl/blob/main/doc/install.MD">Installation</a></li>
+<li><a href="https://github.com/isinaltinkaya/vcfgl/blob/main/doc/depth.MD">Simulating read depths</a></li>
+<li><a href="https://github.com/isinaltinkaya/vcfgl/blob/main/doc/error_qs.MD">Simulating quality score errors</a></li>
+<li><a href="https://github.com/isinaltinkaya/vcfgl/blob/main/doc/with_msprime.MD">Using vcfgl with msprime</a></li>
+<li><a href="https://github.com/isinaltinkaya/vcfgl/blob/main/doc/with_stdpopsim.MD">Using vcfgl with stdpopsim</a></li>
+<li><a href="https://github.com/isinaltinkaya/vcfgl/blob/main/doc/with_SLiM.MD">Using vcfgl with SLiM</a></li>