Move from gitbook to docusaurus, build docs in Travis CI (#10970)

* fix: ignore unknown fields in more RPC responses

* Remove mdbook infrastructure

* Delete gitattributes and other theme related items

Move all docs to /docs folder to support Docusaurus

* all docs need to be moved to /docs

* can be changed in the future

Add Docusaurus infrastructure

* initialize docusaurus repo

Remove trailing whitespace, add support for eslint

Change Docusaurus configuration to support `src`

* No need to rename the folder! Change a setting and we're all good to
go.

* Fixing rebase items

* Remove unneccessary markdown file, fix type

* Some fonts are hard to read. Others, not so much. Rubik, you've been
sidelined. Roboto, into the limelight!

* As much as we all love tutorials, I think we all can navigate around a
markdown file. Say goodbye, `mdx.md`.

* Setup deployment infrastructure

* Move docs job from buildkite to travic

* Fix travis config

* Add vercel token to travis config

* Only deploy docs after merge

* Docker rust env

* Revert "Docker rust env"

This reverts commit f84bc208e807aab1c0d97c7588bbfada1fedfa7c.

* Build CLI usage from docker

* Pacify shellcheck

* Run job on PR and new commits for publication

* Update README

* Fix svg image building

* shellcheck

Co-authored-by: Michael Vines <mvines@gmail.com>
Co-authored-by: Ryan Shea <rmshea@users.noreply.github.com>
Co-authored-by: publish-docs.sh <maintainers@solana.com>

docs/src/css/custom.css

@@ -0,0 +1,69 @@
+/* stylelint-disable docusaurus/copyright-header */
+/**
+ * Any CSS included here will be global. The classic template
+ * bundles Infima by default. Infima is a CSS framework designed to
+ * work well for content-centric websites.
+ */
+
+/* You can override the default Infima variables here. */
+
+@import url('https://fonts.googleapis.com/css2?family=Roboto');
+
+:root {
+  --ifm-color-primary: #25c2a0;
+  --ifm-color-primary-dark: #409088;
+  --ifm-color-primary-darker: #387462;
+  --ifm-color-primary-darkest: #1b4e3f;
+  --ifm-color-primary-light: #42ba96;
+  --ifm-color-primary-lighter: #86b8b6;
+  --ifm-color-primary-lightest: #abd5c6;
+  --ifm-code-font-size: 95%;
+  --ifm-spacing-horizontal: 1em;
+  --ifm-font-family-base: "Roboto", system-ui, -apple-system, Segoe UI, Roboto, Ubuntu, Cantarell, Noto Sans, sans-serif, BlinkMacSystemFont, 'Segoe UI', Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol';
+  --ifm-footer-background-color: #232323;
+}
+
+
+
+
+@keyframes fadeInUp {
+  0% { opacity: 0; transform: translateY(1.5rem); }
+}
+
+main {
+  margin: 1rem 0 5rem 0;
+}
+
+.docusaurus-highlight-code-line {
+  background-color: rgb(72, 77, 91);
+  display: block;
+  margin: 0 calc(-1 * var(--ifm-pre-padding));
+  padding: 0 var(--ifm-pre-padding);
+}
+
+.card {
+  padding: 1rem;
+  margin-top: 2rem;
+  animation: fadeInUp 400ms backwards;
+  animation-delay: 150ms;
+  transition-property: all;
+  transition-duration: 200ms;
+  box-shadow: 0 8px 28px 4px rgba(86,91,115,0.15);
+}
+
+
+.card a {
+  text-decoration: none;
+}
+
+.card:hover {
+  transform: translate(0px, -5px);
+}
+
+.footer--dark {
+  background-color: #232323 !important;
+}
+
+footer .text--center {
+  padding: 2rem 0 0 0;
+}