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

[skip ci]

* 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/css/custom.css

@@ -0,0 +1,18 @@
+.fixedHeaderContainer header img {
+    height: 80%;
+}
+
+@media only screen and (min-device-width: 360px) and (max-device-width: 736px) {
+}
+
+@media only screen and (min-width: 1024px) {
+}
+
+@media only screen and (max-width: 1023px) {
+}
+
+@media only screen and (min-width: 1400px) {
+}
+
+@media only screen and (min-width: 1500px) {
+}