chore: codespell improvements (#1174)

* fix the command so it actually works - see https://github.com/lucasdemarchi/codespell/issues/101
 * check the spelling of more files
 * ignore known-binary filetypes
 * fix a couple of spelling mistakes it caught

Signed-off-by: Juan Cruz Viotti <jviotti@openmailbox.org>

docs/CONTRIBUTING.md

@@ -104,7 +104,7 @@ when your pull request is merged.
 
 - Write a descriptive pull request title.
 
-- Squash commits when possible, for example, when commiting review changes.
+- Squash commits when possible, for example, when committing review changes.
 
 Before your pull request can be merged, the following conditions must hold:
 

lib/gui/components/update-notifier/services/update-notifier.js

@@ -59,7 +59,7 @@ module.exports = function($http, $q, ModalService, UPDATE_NOTIFIER_SLEEP_DAYS, M
         if (error) {
 
           // The error status equals this number if the request
-          // couldn't be made successfuly, for example, because
+          // couldn't be made successfully, for example, because
           // of a timeout on an unstable network connection.
           const ERROR_CODE_UNSUCCESSFUL_REQUEST = -1;
 

package.json

@@ -16,7 +16,7 @@
     "jslint": "eslint lib tests scripts bin versionist.conf.js",
     "sasslint": "sass-lint lib/gui/scss",
     "htmllint": "node scripts/html-lint.js",
-    "codespell": "codespell.py --dictionary=- --dictionary=dictionary lib tests",
+    "codespell": "codespell.py --skip *.gz,*.bz2,*.xz,*.zip,*.img lib tests docs scripts Makefile *.md LICENSE",
     "lint": "npm run jslint && npm run sasslint && npm run codespell && npm run htmllint",
     "changelog": "versionist",
     "start": "electron lib/start.js",