Add postcss-easings

So we can use names like easeInSine in CSS transitions rather than
cubic-bezier(0.47, 0, 0.745, 0.715)

Required for https://github.com/matrix-org/matrix-react-sdk/pull/3674

package.json

@@ -77,6 +77,7 @@
     "matrix-react-sdk": "1.7.3",
     "modernizr": "^3.6.0",
     "olm": "https://packages.matrix.org/npm/olm/olm-3.1.4.tgz",
+    "postcss-easings": "^2.0.0",
     "prop-types": "^15.7.2",
     "react": "^16.9.0",
     "react-dom": "^16.9.0",
@@ -113,8 +114,8 @@
     "eslint": "^5.8.0",
     "eslint-config-google": "^0.7.1",
     "eslint-plugin-babel": "^4.1.2",
-    "eslint-plugin-jest": "^23.0.4",
     "eslint-plugin-flowtype": "^2.50.3",
+    "eslint-plugin-jest": "^23.0.4",
     "eslint-plugin-react": "^7.11.1",
     "eslint-plugin-react-hooks": "^2.2.0",
     "expect": "^1.16.0",

postcss.config.js

@@ -6,6 +6,7 @@ module.exports = {
         require("postcss-extend")(),
         require("postcss-nested")(),
         require("postcss-mixins")(),
+        require("postcss-easings")(),
         require("postcss-strip-inline-comments")(),
     ],
     "parser": "postcss-scss",

yarn.lock

@@ -7164,6 +7164,14 @@ posix-character-classes@^0.1.0:
   resolved "https://registry.yarnpkg.com/posix-character-classes/-/posix-character-classes-0.1.1.tgz#01eac0fe3b5af71a2a6c02feabb8c1fef7e00eab"
   integrity sha1-AerA/jta9xoqbAL+q7jB/vfgDqs=
 
+postcss-easings@^2.0.0:
+  version "2.0.0"
+  resolved "https://registry.yarnpkg.com/postcss-easings/-/postcss-easings-2.0.0.tgz#79bde7ce71c838ef7371a59d293e08b337b1802b"
+  integrity sha512-oJUmnrPwayx47y+jrRKSofHOjRjdJCOyqNXZURQkAVEra93ShqUcN8WYIuT/pWQeGe2I/pxxFfw7mOUGBrxCRQ==
+  dependencies:
+    postcss "^7.0.2"
+    postcss-value-parser "^3.3.0"
+
 postcss-extend@^1.0.5:
   version "1.0.5"
   resolved "https://registry.yarnpkg.com/postcss-extend/-/postcss-extend-1.0.5.tgz#5ea98bf787ba3cacf4df4609743f80a833b1d0e7"