KaTeX website & documentation (#1484)

* website/docs: initial commit

* Change secondaryColor

* Fix index.css not being copied and included on global stylesheet

* Fix stylesheet link

[skip ci]

* Change documentation link to API(Usage)

[skip ci]

* Add `Libraries` in usage

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* Remove documentation from `README.md` and add link to the site

[skip ci]

* Use KaTeX in the parent directory to build Markdown

[skip ci]

* Revise function support page. Avoid error msgs.

* General edit to function support page

website/static/static/index.css

@@ -0,0 +1,212 @@
+body {
+    font: 16px/1.4 "proxima-nova", "Helvetica Neue", Arial, Helvetica, sans-serif;
+}
+
+.container {
+    margin: 0 auto;
+    margin: 0 auto;
+    width: 800px;
+}
+
+.header, .footer {
+    color: #fff;
+    background: #329894;
+    overflow: hidden;
+}
+
+.cta {
+    margin: 10px 0;
+    text-align: center;
+}
+
+.cta a {
+    border-radius: 3px;
+    display: inline-block;
+    font-weight: 600;
+    margin: 0 10px;
+    padding: 8px 24px;
+    text-decoration: none;
+}
+
+.header {
+    padding: 40px 0 0;
+}
+
+.logo {
+    color: #fff;
+    font-size: 45px;
+    margin: 0;
+}
+
+.tagline {
+    font-size: 28px;
+    font-weight: 300;
+    padding: 20px 0;
+    text-align: center;
+}
+
+.tagline em {
+    font-weight: 600;
+}
+
+.header .cta a {
+    border: 3px solid;
+    color: #fff;
+}
+
+.header .cta a:hover {
+    background: rgba(255, 255, 255, 0.1);
+}
+
+.demo {
+    box-shadow: 0 0 10px rgba(0, 0, 0, 0.3);
+    font-size: 22px;
+    margin: 50px 0 0;
+}
+
+.demo,
+.demo-left,
+.demo-right {
+    height: 260px;
+}
+
+.demo-left,
+.demo-right {
+    box-sizing: border-box;
+    float: left;
+    padding: 20px 30px;
+    width: 50%;
+}
+
+.demo-instructions {
+    line-height: 1.5;
+    margin-bottom: 10px;
+    opacity: 0.8;
+}
+
+.demo-left {
+    background: #444;
+}
+
+.demo-left textarea {
+    background: #000;
+    border: none;
+    box-sizing: border-box;
+    color: #fff;
+    font: 14px Menlo, monospace;
+    height: 160px;
+    padding: 10px;
+    resize: none;
+    width: 100%;
+}
+
+.demo-right {
+    background: #fff;
+    color: #444;
+}
+
+#demo-output {
+    font-size: 18px;
+    padding: 10px 0;
+    overflow: auto;
+}
+
+.main {
+    background: #fff2e7;
+    box-shadow: 0 0 10px rgba(0, 0, 0, 0.3);
+    min-height: 400px;
+    position: relative;
+    padding: 30px 0;
+}
+
+.subtagline {
+    color: #329894;
+    font-size: 24px;
+    font-weight: 600;
+    padding: 20px 0;
+    text-align: center;
+}
+
+.features {
+    font-size: 20px;
+    margin: 0 auto;
+    width: 540px;
+}
+
+.features > li {
+    margin: 10px 0;
+}
+
+.main .examples {
+    margin: 40px 0;
+}
+
+.main .example {
+    font-size: 15px;
+    text-align: center;
+    margin: 30px 0;
+}
+
+.main .comparison-labels {
+    width: 100%;
+    height: 40px;
+}
+
+.main .comparison-labels .left,
+.main .comparison-labels .right {
+    box-sizing: border-box;
+    width: 50%;
+    float: left;
+    height: 40px;
+    text-align: center;
+    font-size: 20px;
+}
+
+.main .comparison {
+    background-image: url(../../img/katex-comparison.gif);
+    background-position: 50% 50%;
+    background-size: cover;
+    box-shadow: 0 0 10px rgba(0, 0, 0, 0.3);
+    height: 340px;
+    width: 100%;
+}
+
+.main .cta {
+    padding-top: 50px;
+}
+
+.main .cta a {
+    border: 3px solid;
+    color: #329894;
+}
+
+.main .cta a:hover {
+    background: rgba(50, 152, 148, 0.1);
+}
+
+.footer {
+    padding: 30px 0;
+    font-size: 21px;
+}
+
+.ka-logo {
+    float: right;
+}
+
+.ka-logo img {
+    border: none;
+    vertical-align: -1px;
+}
+
+.credits {
+    float: left;
+    font-size: 16px;
+}
+
+.credits a {
+    color: white;
+}
+
+.errorMessage {
+    color: red;
+}