3686: Update manual for 2021.1 (TrenchBroom#3693)

* 3686: update "Texture Alignment Keyboard Shortcuts" and "The UV Editor"

* 3686: update layer editor documentation

* 3686: remove unused image

* 3686: update create entity context menu image

* 3686: update MoveBrushesToEntity.png

* 3686: fix typo

* 3686: update view preferences docs

* 3686: mention compilation task checkbox

* 3686: add section for map view context menu, and layer context menu

* 3686: update compile dialog screenshot

* 3686: document Map View Context Menu

* 3686: write out layer context menu in text

* 3686: crop ViewPreferences.png

* 3686: fix compilation dialog "test" docs

* 3694: fix back button in manual

Fixes TrenchBroom#3694

* 3686: fix broken links

* 3686: add UV editor toolbar screenshot

app/resources/documentation/manual/default.css

@@ -220,8 +220,6 @@ dl, figure, h1, h2, h3, h4, img, ol, p, pre, table, ul {
 }
 
 body {
-	display: flex;
-	height: 100vh;
 	color: #333;
 }
 
@@ -232,9 +230,16 @@ body > main, body > nav, body > section {
 }
 
 body #toc {
-	min-width: -webkit-max-content;
-	min-width: -moz-max-content;
-	min-width: max-content;
+	/* Use fixed positioning instead of flexbox,
+	until we can figure out a better fix for https://github.com/TrenchBroom/TrenchBroom/issues/3694
+	*/
+	width: 300px;
+	overflow-y: auto;
+	overflow-x: hidden;
+	position: fixed;
+	top: 0;
+	bottom: 0;
+
 	font-family: -apple-system, BlinkMacSystemFont, Segoe UI, Roboto, Helvetica Neue, Arial, sans-serif, Apple Color Emoji, Segoe UI Emoji, Segoe UI Symbol, Noto Color Emoji;
 	font-size: 16px;
 	-webkit-user-select: none;
@@ -291,6 +296,7 @@ body #toc_inner > ul > li > a {
 }
 
 body #content {
+	margin-left: 300px; /* #toc width */
 	overflow: auto;
 	font-family: -apple-system, BlinkMacSystemFont, Segoe UI, Roboto, Helvetica Neue, Arial, sans-serif, Apple Color Emoji, Segoe UI Emoji, Segoe UI Symbol, Noto Color Emoji;
 	font-size: 16px;
@@ -323,6 +329,10 @@ body #content_version p span:first-child::before {
 }
 
 @media (max-width: 768px) {
+	body #content {
+		margin-left: 0px; /* #toc width */
+	}
+
 	body #toc {
 		display: none;
 		width: 100vw;