Jackson 3 series companion code

37 runnable examples covering the eight feature posts on ankurm.com, verified
against Jackson 3.2.1 on Temurin 21.0.5. Every output committed under docs/ was
produced by run-all.sh.

Also documents 11 places where the published snippets do not compile or do not
behave as printed against a real Jackson 3 build - most notably that
writeValueAsString(List<Base>) silently drops the polymorphic type discriminator,
so the post's serialised output cannot be read back.

docs/output/B01WriteJson.txt

@@ -0,0 +1,8 @@
+{"articleId":1,"title":"Jackson Deep Dive","tags":["java","json"]}
+file     : {"articleId":1,"title":"Jackson Deep Dive","tags":["java","json"]}
+pretty   :
+{
+  "articleId" : 1,
+  "title" : "Jackson Deep Dive",
+  "tags" : [ "java", "json" ]
+}