🧘🏼‍♀️ flexibility (#22)

* update functionality.

* add example project.

* handle empty facebook and twitter fields.

* testing overrides.

* fix twitter bug. update docs.

* fix twitter bug. update docs.

* lint and format.

.eslintignore

@@ -0,0 +1,15 @@
+# editor
+.vscode
+
+# dependencies
+.cache
+node_modules
+
+# build
+public
+
+# host
+.netlify
+
+# secrets
+.env*

example/gatsby-config.js

@@ -0,0 +1,6 @@
+module.exports = {
+    siteMetadata: {
+        title: "Gatsby Default Starter",
+    },
+    plugins: ["gatsby-plugin-react-helmet"],
+}

example/package.json

@@ -0,0 +1,38 @@
+{
+    "name": "gatsby-starter-default",
+    "private": true,
+    "description": "A simple starter to get up and developing quickly with Gatsby",
+    "version": "0.1.0",
+    "author": "Kyle Mathews <[email protected]>",
+    "dependencies": {
+        "gatsby": "^3.11.0",
+        "gatsby-plugin-react-helmet": "^4.11.0",
+        "gatsby-source-filesystem": "^3.11.0",
+        "gatsby-transformer-sharp": "^3.11.0",
+        "prop-types": "^15.7.2",
+        "react": "^17.0.1",
+        "react-dom": "^17.0.1",
+        "react-helmet": "^6.1.0"
+    },
+    "devDependencies": {
+        "prettier": "2.3.2"
+    },
+    "keywords": [
+        "gatsby"
+    ],
+    "license": "0BSD",
+    "scripts": {
+        "build": "gatsby build",
+        "develop": "gatsby develop",
+        "start": "npm run develop",
+        "serve": "gatsby serve",
+        "clean": "gatsby clean"
+    },
+    "repository": {
+        "type": "git",
+        "url": "https://github.com/gatsbyjs/gatsby-starter-default"
+    },
+    "bugs": {
+        "url": "https://github.com/gatsbyjs/gatsby/issues"
+    }
+}

example/src/components/header.js

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+import {Link} from "gatsby"
+import PropTypes from "prop-types"
+import * as React from "react"
+
+const Header = ({siteTitle}) => (
+    <header
+        style={{
+            background: "rebeccapurple",
+            marginBottom: "1.45rem",
+        }}
+    >
+        <div
+            style={{
+                margin: "0 auto",
+                maxWidth: 960,
+                padding: "1.45rem 1.0875rem",
+            }}
+        >
+            <h1 style={{margin: 0}}>
+                <Link
+                    to="/"
+                    style={{
+                        color: "white",
+                        textDecoration: "none",
+                    }}
+                >
+                    {siteTitle}
+                </Link>
+            </h1>
+        </div>
+    </header>
+)
+
+Header.propTypes = {
+    siteTitle: PropTypes.string,
+}
+
+Header.defaultProps = {
+    siteTitle: "",
+}
+
+export default Header