add a changelog to track converse source changes

CHANGELOG.md

+# CHANGELOG
+
+This file contains the changes applied to the sources of converse<br>
+The current build version of converse is: `v7.0.3dev`<br>
+If the converse sources have to be updated, apply these changes again, or fix them using plugins
+
+### 2021-03-12
+* Added the `fa-reply` icon into the icons svg (icons.js)
+
+### 2021-03-02
+* Fixed the date separator format for French language
+
+### 2021-02-18
+* Added support for custom HTTP headers in file upload
+* Allowed the preview of webp images in messages
+* Disabled the image modal in messages
+
+### 2021-02-15
+* Escaped an error on undefined `ev.target` when scrolling a chat view
+* Fixed missing default avatar by updating its image type to webp
+
+### 2021-02-08
+* Disabled the user modal on avatars (in messages)
+
+### 2021-02-04
+* Fixed @ mention on new lines
+
+### 2021-01-25
+* Updated the default avatar image