Merge branch 'es/first-contrib-tutorial' into pu

A WIP of a new tutorial targetting specifically aspiring git-core
developers.

* es/first-contrib-tutorial:
  documentation: add lab for first contribution

Author: gitster

Documentation/Makefile

@@ -77,6 +77,7 @@ API_DOCS = $(patsubst %.txt,%,$(filter-out technical/api-index-skel.txt technica
 SP_ARTICLES += $(API_DOCS)
 
 TECH_DOCS += SubmittingPatches
+TECH_DOCS += MyFirstContribution
 TECH_DOCS += technical/hash-function-transition
 TECH_DOCS += technical/http-protocol
 TECH_DOCS += technical/index-format