docs: Update environment sections

Fix links in markdown, and add details about
Wayland environment variables.

docs/reference/gtk/running.md

@@ -4,9 +4,10 @@
 
 GTK inspects a number of environment variables in addition to
 standard variables like `LANG`, `PATH`, `HOME` or `DISPLAY`; mostly
-to determine paths to look for certain files. The [X11]{#x11-envar},
-[Windows]{#win32-envar} and [Broadway]{#broadway-envar} GDK backends
-use some additional environment variables.
+to determine paths to look for certain files. The [X11](#x11-envar),
+[Wayland](#wayland-envar), [Windows](#win32-envar) and
+[Broadway](#broadway-envar) GDK backends use some additional
+environment variables.
 
 ### GTK_DEBUG {#GTK_Debug-Options}
 

docs/reference/gtk/wayland.md

@@ -7,4 +7,13 @@ the Wayland backend by setting `GDK_BACKEND=wayland`.
 On UNIX, the Wayland backend is enabled by default, so you don't need to
 do anything special when compiling it, and everything should "just work."
 
-Currently, the Wayland backend does not use any additional environment variables.
+## Wayland-specific environment variables {#wayland-envar}
+
+### WAYLAND_DISPLAY
+
+Specifies the name of the Wayland display to use. Typically, wayland-0
+or wayland-1.
+
+### XDG_RUNTIME_DIR
+
+Used to locate the Wayland socket to use.

docs/reference/gtk/windows.md

@@ -16,7 +16,6 @@ variables.
 ### GDK_IGNORE_WINTAB
 
 If this variable is set, GTK doesn't use the Wintab API for tablet support.
-</para>
 
 ### GDK_USE_WINTAB
 
@@ -37,10 +36,10 @@ can override GTK settings in the `settings.ini` file or at runtime in the
 GTK Inspector.
 
 Themes are loaded from normal Windows variants of the XDG locations:
-`%HOME%/icons/THEME/cursors`, 
-`%APPDATA%/icons/THEME/cursors`, 
+`%HOME%/icons/THEME/cursors`,
+`%APPDATA%/icons/THEME/cursors`,
 `RUNTIME_PREFIX/share/icons/THEME/cursors`
 
-The `gtk-cursor-theme-size`> setting is ignored, GTK will use
+The `gtk-cursor-theme-size` setting is ignored, GTK will use
 the cursor size that Windows tells it to use.