Bump to 0.31.1, update changelog

Author: jgm

changelog.txt

@@ -1,3 +1,14 @@
+[0.31.1]
+
+  * Fix HTML comment parsing with `-` before closing `-->`
+    (#285, Robin Stocker).
+  * Accept lowercase inline HTML declarations (Michael Howell).
+  * Fix title-related backtracking with empty string (#281,
+    Michael Howell).
+  * Remove `string.prototype.repeat` polyfill (Steven).
+  * Remove `source`, add `search` to list of recognized block tags.
+    (a spec 0.31 change we forgot in last release).
+
 [0.31.0]
 
   * Update to 0.31 spec.txt.

package.json

@@ -1,7 +1,7 @@
 {
   "name": "commonmark",
   "description": "a strongly specified, highly compatible variant of Markdown",
-  "version": "0.31.0",
+  "version": "0.31.1",
   "homepage": "https://commonmark.org",
   "keywords": [
     "markdown",