Pixel: update font sizes and weights (#6479)

* Update paragraph styles.

* Update heading sizes.

* Update site title and post title fonts and weights.

* Enable fluid for the standard medium size.

* Update heading weights.

* Update site title weight.

* Update fluid type scale to use same viewport as Gutenberg.

pixel/theme.json

@@ -73,6 +73,7 @@
             ]
         },
         "typography": {
+            "fluid": true,
             "fontFamilies": [
                 {
                     "fontFamily": "'DM Mono', sans-serif",
@@ -145,21 +146,28 @@
             "fontSizes": [
                 {
                     "name": "Small",
-                    "size": "1rem",
+                    "size": ".813rem",
+                    "fluid": false,
                     "slug": "small"
                 },
                 {
                     "name": "Medium",
-                    "size": "1.5rem",
+                    "size": "1.125rem",
+                    "fluid": {
+                        "min": "1rem",
+                        "max": "1.125rem"
+                    },
                     "slug": "medium"
                 },
                 {
                     "name": "Large",
-                    "size": "1.75rem",
+                    "fluid": false,
+                    "size": "1.5rem",
                     "slug": "large"
                 },
                 {
                     "name": "Extra Large",
+                    "fluid": false,
                     "size": "2rem",
                     "slug": "x-large"
                 }
@@ -267,7 +275,8 @@
                     }
                 },
                 "typography": {
-                    "fontSize": "var(--wp--preset--font-size--large)",
+                    "fontSize": "clamp(1.375rem, 1.2916666666666667rem + 0.4166666666666667vw, 1.625rem)",
+                    "fontWeight": "normal",
                     "lineHeight": "1.125"
                 }
             },
@@ -328,8 +337,9 @@
             },
             "core/site-title": {
                 "typography": {
-                    "fontSize": "1.125rem",
-                    "fontWeight": "700",
+                    "fontSize": "0.875rem",
+                    "fontWeight": "400",
+                    "textTransform": "uppercase",
                     "textDecoration": "none"
                 }
             }
@@ -362,34 +372,42 @@
 					}
 				}
 			},
+            "heading": {
+                "typography": {
+                    "fontWeight": "500"
+                }
+            },
             "h1": {
                 "typography": {
-                    "fontSize": "3rem"
+                    "fontSize": "clamp(1.375rem, 1.1442307692307692rem + 0.4807692307692308vw, 1.625rem)"
                 }
             },
             "h2": {
                 "typography": {
-                    "fontSize": "var(--wp--preset--font-size--x-large)"
+                    "fontSize": "clamp(1.25rem, 1.1346153846153846rem + 0.2403846153846154vw, 1.375rem)"
                 }
             },
             "h3": {
                 "typography": {
-                    "fontSize": "var(--wp--preset--font-size--large)"
+                    "fontSize": "clamp(1.125rem, 1.0096153846153846rem + 0.2403846153846154vw, 1.25rem)"
                 }
             },
             "h4": {
                 "typography": {
-                    "fontSize": "var(--wp--preset--font-size--medium)"
+                    "fontSize": "1.125rem"
                 }
             },
             "h5": {
                 "typography": {
-                    "fontSize": "1.125rem"
+                    "fontSize": "0.813rem",
+                    "textTransform": "uppercase"
                 }
             },
             "h6": {
                 "typography": {
-                    "fontSize": "var(--wp--preset--font-size--small)"
+                    "fontSize": "0.75rem",
+                    "fontWeight": "400",
+                    "textTransform": "uppercase"
                 }
             },
             "link": {