Add a README.

README.md

@@ -0,0 +1,48 @@
+__mal-decimal-scores__ is a Google Chrome extension that allows you to give
+decimal scores for your anime on [MyAnimeList](http://myanimelist.net/).
+
+When enabled, the normal 1-10 system is replaced with one from 1.0 to 10.0.
+Rounded integer scores are saved on MyAnimeList as usual, and decimal scores
+are saved using [Chrome sync](https://developer.chrome.com/extensions/storage)
+so that they are available on any device you have using Chrome.
+
+## Installing
+
+Currently, the extension is not available in packaged form. This may change in
+the future.
+
+To install it from source, first clone the repository into a permanent
+location. Then, go to [chrome://extensions](chrome://extensions), enable the
+"Developer mode" checkbox in the top right corner, click on "Load unpackaged
+extension...", and choose the directory of the git repository.
+
+You will need to pack the extension yourself if you want scores to be synced
+between multiple computers. Click on the "Pack extension..." button and choose
+the git repository directory as the extension root. After the extension is
+packed, open the resulting `.crx` file in all copies of Chrome that you want to
+share the same set of scores.
+
+## Usage
+
+Usage should be mostly straightforward – in any place where you would
+previously rate an anime by selecting a score from a dropdown menu, you can now
+enter a number. Decimal scores are enabled on your list page, individual anime
+pages, pages where you can add to/edit your list, and the "shared anime" page.
+
+Scores can be exported by going to the standard list
+[export page](http://myanimelist.net/panel.php?go=export), which will cause a
+`animelist_decimal_scores.json` file to be downloaded to your computer. Scores
+can be loaded from this file by going to the
+[import page](http://myanimelist.net/import.php).
+
+## Caveats
+
+- Only anime can be given decimal scores. Manga scores are not affected.
+
+- As noted above, only you can see your decimal scores. Others will see your
+  scores rounded to integer values.
+
+- Due to data restrictions in Chrome sync, there is an upper limit to the
+  number of anime you can give a decimal score. This limit should be no less
+  than a few thousand titles. You can check your data usage by going to the
+  [export page](http://myanimelist.net/panel.php?go=export).