Use sentence case for headings

storybook/src/foundation/design-tokens/text.docs.mdx

@@ -8,7 +8,7 @@ import { Meta, Typeset } from "@storybook/blocks";
 
 ## Size
 
-### Seven Text Levels
+### Seven text levels
 
 There are 7 levels of text size and corresponding line height.
 Each typographic element belongs to one of these levels: heading, paragraph, link, quote, form text, etc.
@@ -42,7 +42,7 @@ All text sizes are derived from four foundational values: two text sizes and two
 2. The multiplication between text levels at either of these window widths.
    They are different to let the size of headings increase slower on smaller screens.
 
-### Two Themes for Websites and Applications
+### Two themes for websites and applications
 
 #### Spacious
 
@@ -95,7 +95,7 @@ And the minimum:
   sampleText="Jouw typograaf biedt mij zulke exquise schreven"
 />
 
-### Window Widths for Design
+### Window widths for design
 
 In practice, a window can have any width.
 Designing for all those widths is impractical.
@@ -201,13 +201,13 @@ Exceptions:
 1. The label of a button is centred.
 2. In a table, it might be better to centre or right-align text.
 
-### Line Length
+### Line length
 
 Long lines of text are challenging to read.
 Around 80 characters per line is the maximum.
 In the 12-column [grid](/docs/components-layout-grid--docs), paragraphs meet this when they occupy 8 columns or fewer.
 
-### Word Breaking
+### Word breaking
 
 The Dutch language has many long words, such as ‘gemeenteraadsverkiezingen’ (municipal elections).
 Ensure in your application that these words are hyphenated neatly and do not break out of their container or get hidden.