Force containers to be desktop width

This also adds the ability to override bulma variables, with others defined by bulma

static/src/scss/_bulma_overrides.scss

@@ -0,0 +1,3 @@
+@use "bulma/sass/utilities/initial-variables" as *;
+
+$container-max-width: $widescreen;

static/src/scss/base.scss

@@ -1,4 +1,5 @@
-@import "variables";
+@use "variables" as *;
+@use "bulma_overrides" as *;
 
 @import "bulma/bulma";