Add font-weight to body styles (#2871)

* Add font-weight to body styles

Add default font-weight to body styles

* add changeset

Author: lukasoppermann

.changeset/short-falcons-march.md

@@ -0,0 +1,5 @@
+---
+'@primer/css': patch
+---
+
+Add default font weight (--base-text-weight-normal, 400) to body

src/base/base.scss

@@ -15,6 +15,7 @@ button {
 body {
   font-family: $body-font;
   font-size: var(--body-font-size, $body-font-size);
+  font-weight: var(--base-text-weight-normal, 400);
   line-height: $body-line-height;
   color: var(--fgColor-default, var(--color-fg-default));
   background-color: var(--bgColor-default, var(--color-canvas-default));