tast: Add headings to test_dependencies.md.

Add a few headings to test_dependencies.md to make the
example changes easier to find.

BUG=none
TEST=none

Change-Id: If7502fff10fdd37373c28c4ab0a0bf097ca318c1
Reviewed-on: https://chromium-review.googlesource.com/c/1448885
Tested-by: Dan Erat <[email protected]>
Reviewed-by: Ricardo Quesada <[email protected]>
diff --git a/docs/test_dependencies.md b/docs/test_dependencies.md
index 4099181..2049086 100644
--- a/docs/test_dependencies.md
+++ b/docs/test_dependencies.md
@@ -61,6 +61,8 @@
 Before a new USE flag can be used in an expression, it must be added to `IUSE`
 in the [tast-use-flags] package.
 
+## Example changes
+
 See the following changes for an example of adding a new `containers` software
 feature based on the `containers` USE flag and making a test depend on it:
 
@@ -68,8 +70,10 @@
 *   `tast` repository: <https://crrev.com/c/1382621>
 *   `tast-tests` repository: <https://crrev.com/c/1382878>
 
-The exception to the above are `autotest-capability:`-prefixed features, which
-are added by the [autocaps package] as specified by YAML files in
+## autotest-capability
+
+Exceptions to the above are `autotest-capability:`-prefixed features, which are
+added by the [autocaps package] as specified by YAML files in
 `/usr/local/etc/autotest-capability`. This exists in order to support porting
 existing Autotest-based video tests to Tast. Do not depend on capabilities from
 outside of video tests.