Adds BLM banner (#2454)

Summary:
**Summary**

Adds a Black Lives Matter banner like other OSS projects of the React family

**Test Plan**

Local tests

```
cd website
yarn
yarn start
```

## Screenshots
<img width="752" alt="Screen Shot 2020-06-02 at 21 10 00" src="https://user-images.githubusercontent.com/860099/83565342-2a8d7a80-a516-11ea-9eb8-697f1f781a4c.png">

<img width="1392" alt="Screen Shot 2020-06-02 at 21 09 18" src="https://user-images.githubusercontent.com/860099/83565335-26615d00-a516-11ea-8e6f-cad0d3f3cc2f.png">

<img width="1072" alt="Screen Shot 2020-06-02 at 21 10 07" src="https://user-images.githubusercontent.com/860099/83565349-2bbea780-a516-11ea-85d8-c9da292998c7.png">
Pull Request resolved: #2454

Reviewed By: mrkev

Differential Revision: D21849517

Pulled By: claudiopro

fbshipit-source-id: c4b8944b7cbfbe9603bde4ad5128f3826ecb1f04

website/src/css/custom.css

@@ -13,6 +13,21 @@
   --ifm-color-primary-light: rgb(150, 80, 80);
   --ifm-color-primary-lighter: rgb(169, 111, 111);
   --ifm-color-primary-lightest: rgb(194, 152, 152);
-
   --ifm-code-font-size: 95%;
 }
+
+.navbar {
+  filter: grayscale(100%);
+}
+
+.menu {
+  filter: grayscale(100%);
+}
+
+.hero {
+  filter: grayscale(100%);
+}
+
+.container {
+  filter: grayscale(100%);
+}

website/src/pages/index.js

@@ -31,6 +31,16 @@ function Home() {
 
   return (
     <Layout permalink="/" description={siteConfig.tagline}>
+      <div className={styles.blm}>
+        Black Lives Matter.{' '}
+        <a
+          target="_blank"
+          rel="noopener"
+          rel="noreferrer"
+          href="https://support.eji.org/give/153413/#!/donation/checkout">
+          Support&nbsp;the&nbsp;Equal&nbsp;Justice&nbsp;Initiative.
+        </a>
+      </div>
       <div className="hero hero--primary shadow--lw">
         <div className="container">
           <div className="row">

website/src/pages/styles.module.css

@@ -5,6 +5,13 @@
  * LICENSE file in the root directory of this source tree.
  */
 
+.blm {
+  font-size: 20px;
+  height: 80px;
+  padding: 20px;
+  text-align: center;
+}
+
 @media only screen and (max-width: 996px) {
   .demoGif {
     margin-top: 2rem;
@@ -14,4 +21,8 @@
   .hideOnTabletAndSmaller {
     display: none;
   }
+
+  .blm {
+    height: 70px;
+  }
 }