Docs: Add commit-graph tech docs to Makefile

Ensure that the commit-graph.txt and commit-graph-format.txt files
are compiled to HTML using ASCIIDOC.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>

Author: derrickstolee

Documentation/Makefile

@@ -69,6 +69,8 @@ API_DOCS = $(patsubst %.txt,%,$(filter-out technical/api-index-skel.txt technica
 SP_ARTICLES += $(API_DOCS)
 
 TECH_DOCS += SubmittingPatches
+TECH_DOCS += technical/commit-graph
+TECH_DOCS += technical/commit-graph-format
 TECH_DOCS += technical/hash-function-transition
 TECH_DOCS += technical/http-protocol
 TECH_DOCS += technical/index-format