MNT: Update Changelog to 0.5.2

Author: kernc

CHANGELOG

@@ -1,3 +1,21 @@
+0.5.2
+=====
+  - Add `__main__.py` so users can invoke `python -m pdoc`.
+  - Fix: List builtin class method descriptors
+  - Google docstring format fixes:
+    - Support for 2-space indents.
+    - Recognize sections even when not preceded by an empty line.
+    - Recognize additional characters (`,=[]`) in type specifications.
+  - HTML template fixes:
+    - Fixed some CSS typos.
+    - Re-styled View Source button in HTML template.
+    - Two-column TOC reference lists only when all names are short.
+    - TOC links for some class no longer lead to its ancestor class.
+
+0.5.1
+=====
+  - Markdown >= 3.0.0 requirement.
+
 0.5.0
 =====
   - Relicensed as AGPL-3.0.