Replace bold with headings in breaking changes pages (#2774)

* Replace bold with headings in breaking changes pages
  (keep the linter happy at all costs)
* Group breaking changes by impact
* Fix some issues

Author: roji

.markdownlint.json

@@ -5,6 +5,5 @@
     "MD025": { "front_matter_title": "" },
     "MD027": false,
     "MD028": false,
-    "MD033": { "allowed_elements": ["sup", "sub", "nobr", "span", "a"] },
-    "MD036": false
+    "MD033": { "allowed_elements": ["sup", "sub", "nobr", "span", "a"] }
 }

.vscode/settings.json

@@ -11,9 +11,11 @@
     ],
     "cSpell.words": [
         "LINQ",
+        "dbcontext",
         "mitigations",
         "navigations",
         "parameterizable",
+        "pluralizer",
         "queryable",
         "savepoint",
         "savepoints",