Add tests for self-references

Note as there is no support for block references at the moment, the generated link goes nowhere, however it is to a reasonable ID

tests/testdata/expected/main-samples/section-ref-a.md

@@ -0,0 +1,7 @@
+[This is a header](section-ref-a.md#this-is-a-header)
+
+[^dda637](section-ref-a.md#dda637)
+
+## This is a header
+
+This is a block ^dda637

tests/testdata/expected/main-samples/section-ref-b.md

@@ -0,0 +1,2 @@
+[section-ref-a > This is a header](section-ref-a.md#this-is-a-header)
+[section-ref-a > ^dda637](section-ref-a.md#dda637)

tests/testdata/input/main-samples/section-ref-a.md

@@ -0,0 +1,7 @@
+[[#This is a header]]
+
+[[#^dda637]]
+
+## This is a header
+
+This is a block ^dda637

tests/testdata/input/main-samples/section-ref-b.md

@@ -0,0 +1,2 @@
+[[section-ref-a#This is a header]]
+[[section-ref-a#^dda637]]