Fix text-lg variable and use text-lg for dropdown title

Author: reakaleek

src/Elastic.Documentation.Site/Assets/markdown/dropdown.css

@@ -7,7 +7,7 @@
 		details.dropdown {
 			@apply border-grey-20 mt-4 block rounded-sm border-1 shadow-xs;
 			summary.dropdown-title {
-				@apply text-ink-dark flex cursor-pointer items-stretch justify-between font-sans text-xl font-bold;
+				@apply text-ink-dark flex cursor-pointer items-stretch justify-between font-sans text-lg font-bold;
 			}
 
 			&[open] .dropdown-title {

src/Elastic.Documentation.Site/Assets/theme.css

@@ -180,6 +180,7 @@
 	--text-xs: 0.857rem; /* 12px */
 	--text-sm: 1rem; /* 14px */
 	--text-base: 1.143rem; /* 16px */
+	--text-lg: 1.286rem; /* 18px */
 	--text-xl: 1.429rem; /* 20px */
 	--text-2xl: 1.714rem; /* 24px */
 	--text-3xl: 2.143rem; /* 30px */