Refine/add message[-*] icons (#1208)

* Add `message-square-warning` icon

* Optimise `message-square-plus` icon

* Add `message-square-diff` (request changes) icon

* Refine `message-circle` icon

* Add `message-circle-question` icon

* Add `message-circle-warning` icon

* Add `message-square-x` icon

* Add `message-square-off` icon

* Add `message-circle-plus` icon

* Add `message-circle-x` icon

* Add `message-circle-off` icon

* Refine `message-circle` icons

* Fix `message-circle-question` mark

* Fix `message-square-diff` icon

* Add `message-square-share` icon

* Add `message-square-text` icon

* Refine `message-square-x` icon

* Add `message-square-code` icon

* Improve `message-*` icons metadata

* Add `message-square-more` icon

* Improve `more-horizontal` metadata

* Add `message-circle-more` icon

* Add `message-circle-dashed` icon

* Add `message-square-text-quote` icon

* Add `message-square-quote` icon

* Add `message-square-reply` icon

* Add `message-circle-code` icon

* Add `message-circle-reply` icon

* Add `message-circle-heart` icon

* Add `message-square-heart` icon

* Add `message-square-dot` (unread) icon

* Add `message-square-dot-big` (unread/notification) variant

* Remove message-square-text-quote and rename message-square-dot-big

* Added as contributor in meta data

---------

Co-authored-by: Eric Fennis <eric.fennis@gmail.com>

icons/message-square-diff.json

@@ -0,0 +1,31 @@
+{
+  "$schema": "../icon.schema.json",
+  "contributors": [
+    "danielbayley"
+  ],
+  "tags": [
+    "comment",
+    "chat",
+    "conversation",
+    "dialog",
+    "feedback",
+    "speech bubble",
+    "add",
+    "patch",
+    "difference",
+    "plus",
+    "minus",
+    "plus-minus",
+    "maths",
+    "code review",
+    "coding",
+    "version control",
+    "git"
+  ],
+  "categories": [
+    "development",
+    "files",
+    "account",
+    "social"
+  ]
+}