Move 3rd party js/css into public/vendor and document sources (#2383)

This commit cherry picks the following commits (master -> v1.2):
  a915a09
  874f9be
  233bbcf

Ref: https://github.com/go-gitea/gitea/issues/1484
Signed-off-by: Michael Lustfield <michael@lustfield.net>

public/vendor/plugins/highlight/LICENSE

@@ -0,0 +1,25 @@
+Copyright (c) 2006, Ivan Sagalaev
+All rights reserved.
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+    * Redistributions in binary form must reproduce the above copyright
+      notice, this list of conditions and the following disclaimer in the
+      documentation and/or other materials provided with the distribution.
+    * Neither the name of highlight.js nor the names of its contributors 
+      may be used to endorse or promote products derived from this software 
+      without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND ANY
+EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE REGENTS AND CONTRIBUTORS BE LIABLE FOR ANY
+DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+

public/vendor/plugins/highlight/default.css

@@ -0,0 +1,99 @@
+/*
+
+Original highlight.js style (c) Ivan Sagalaev <maniac@softwaremaniacs.org>
+
+*/
+
+.hljs {
+  display: block;
+  overflow-x: auto;
+  padding: 0.5em;
+  background: #F0F0F0;
+}
+
+
+/* Base color: saturation 0; */
+
+.hljs,
+.hljs-subst {
+  color: #444;
+}
+
+.hljs-comment {
+  color: #888888;
+}
+
+.hljs-keyword,
+.hljs-attribute,
+.hljs-selector-tag,
+.hljs-meta-keyword,
+.hljs-doctag,
+.hljs-name {
+  font-weight: bold;
+}
+
+
+/* User color: hue: 0 */
+
+.hljs-type,
+.hljs-string,
+.hljs-number,
+.hljs-selector-id,
+.hljs-selector-class,
+.hljs-quote,
+.hljs-template-tag,
+.hljs-deletion {
+  color: #880000;
+}
+
+.hljs-title,
+.hljs-section {
+  color: #880000;
+  font-weight: bold;
+}
+
+.hljs-regexp,
+.hljs-symbol,
+.hljs-variable,
+.hljs-template-variable,
+.hljs-link,
+.hljs-selector-attr,
+.hljs-selector-pseudo {
+  color: #BC6060;
+}
+
+
+/* Language color: hue: 90; */
+
+.hljs-literal {
+  color: #78A960;
+}
+
+.hljs-built_in,
+.hljs-bullet,
+.hljs-code,
+.hljs-addition {
+  color: #397300;
+}
+
+
+/* Meta color: hue: 200 */
+
+.hljs-meta {
+  color: #1f7199;
+}
+
+.hljs-meta-string {
+  color: #4d99bf;
+}
+
+
+/* Misc effects */
+
+.hljs-emphasis {
+  font-style: italic;
+}
+
+.hljs-strong {
+  font-weight: bold;
+}

public/vendor/plugins/highlight/github.css

@@ -0,0 +1,99 @@
+/*
+
+github.com style (c) Vasily Polovnyov <vast@whiteants.net>
+
+*/
+
+.hljs {
+  display: block;
+  overflow-x: auto;
+  padding: 0.5em;
+  color: #333;
+  background: #f8f8f8;
+}
+
+.hljs-comment,
+.hljs-quote {
+  color: #998;
+  font-style: italic;
+}
+
+.hljs-keyword,
+.hljs-selector-tag,
+.hljs-subst {
+  color: #333;
+  font-weight: bold;
+}
+
+.hljs-number,
+.hljs-literal,
+.hljs-variable,
+.hljs-template-variable,
+.hljs-tag .hljs-attr {
+  color: #008080;
+}
+
+.hljs-string,
+.hljs-doctag {
+  color: #d14;
+}
+
+.hljs-title,
+.hljs-section,
+.hljs-selector-id {
+  color: #900;
+  font-weight: bold;
+}
+
+.hljs-subst {
+  font-weight: normal;
+}
+
+.hljs-type,
+.hljs-class .hljs-title {
+  color: #458;
+  font-weight: bold;
+}
+
+.hljs-tag,
+.hljs-name,
+.hljs-attribute {
+  color: #000080;
+  font-weight: normal;
+}
+
+.hljs-regexp,
+.hljs-link {
+  color: #009926;
+}
+
+.hljs-symbol,
+.hljs-bullet {
+  color: #990073;
+}
+
+.hljs-built_in,
+.hljs-builtin-name {
+  color: #0086b3;
+}
+
+.hljs-meta {
+  color: #999;
+  font-weight: bold;
+}
+
+.hljs-deletion {
+  background: #fdd;
+}
+
+.hljs-addition {
+  background: #dfd;
+}
+
+.hljs-emphasis {
+  font-style: italic;
+}
+
+.hljs-strong {
+  font-weight: bold;
+}