feat(www): seo improvements (#13829)

* seo improvements

* prettier fix

Author: krunalcodes

www/src/pages/plugins.js

@@ -1,4 +1,5 @@
 import React, { Component } from "react"
+import { Helmet } from "react-helmet"
 import Container from "../components/container"
 import Rotator from "../components/rotator"
 import { Link } from "gatsby"
@@ -11,6 +12,9 @@ class Plugins extends Component {
   render() {
     return (
       <>
+        <Helmet>
+          <title>Plugins</title>
+        </Helmet>
         <Container
           overrideCSS={{
             alignItems: `center`,

www/src/templates/tags.js

@@ -1,4 +1,5 @@
 import React from "react"
+import { Helmet } from "react-helmet"
 import { graphql } from "gatsby"
 import TagsIcon from "react-icons/lib/ti/tags"
 
@@ -29,6 +30,9 @@ const Tags = ({ pageContext, data, location }) => {
 
   return (
     <Layout location={location}>
+      <Helmet>
+        <title>{tags}</title>
+      </Helmet>
       <Container>
         <h1>{tagHeader}</h1>
         <Button small key="blog-post-view-all-tags-button" to="/blog/tags">

www/src/templates/template-contributor-page.js

@@ -1,4 +1,5 @@
 import React from "react"
+import { Helmet } from "react-helmet"
 import { graphql } from "gatsby"
 import Img from "gatsby-image"
 
@@ -16,6 +17,29 @@ class ContributorPageTemplate extends React.Component {
     return (
       <Layout location={this.props.location}>
         <main>
+          <Helmet>
+            <title>{contributor.id}</title>
+            <meta name="description" content={contributor.bio} />
+            <meta property="og:description" content={contributor.bio} />
+            <meta name="twitter:description" content={contributor.bio} />
+            <meta property="og:title" content={contributor.id} />
+            {contributor.avatar && (
+              <meta
+                property="og:image"
+                content={`https://gatsbyjs.org${
+                  contributor.avatar.childImageSharp.fixed.src
+                }`}
+              />
+            )}
+            {contributor.avatar && (
+              <meta
+                name="twitter:image"
+                content={`https://gatsbyjs.org${
+                  contributor.avatar.childImageSharp.fixed.src
+                }`}
+              />
+            )}
+          </Helmet>
           <Container>
             <div
               css={{