fix(inlineStyles): case insensitive style props (#1797)

Style property names are case-insensitive, for example `fill`, `FILL`,
and `FiLl` are all valid but refer to the same property. So when
inlining styles, we compare the lowercase strings and only use the last
instance of the property rather than embed them all.

plugins/inlineStyles.js

@@ -252,7 +252,7 @@ exports.fn = (root, params) => {
             csstree.walk(styleDeclarationList, {
               visit: 'Declaration',
               enter(node, item) {
-                styleDeclarationItems.set(node.property, item);
+                styleDeclarationItems.set(node.property.toLowerCase(), item);
               },
             });
             // merge declarations

test/regression.js

@@ -36,8 +36,6 @@ const runTests = async ({ list }) => {
       name === 'w3c-svg-11-test-suite/svg/filters-composite-05-f.svg' ||
       // removing wrapping <g> breaks :first-child pseudo-class
       name === 'w3c-svg-11-test-suite/svg/styling-pres-04-f.svg' ||
-      // messed case insensitivity while inlining styles
-      name === 'w3c-svg-11-test-suite/svg/styling-css-10-f.svg' ||
       // rect is converted to path which matches wrong styles
       name === 'w3c-svg-11-test-suite/svg/styling-css-08-f.svg' ||
       // external image