feat(postcss): mock plugin types (#2930)

Co-authored-by: Dominik Pschenitschni <mail@celement.de>
Reviewed-on: #2930
Co-authored-by: Dominik Pschenitschni <dpschen@noreply.kolaente.de>
Co-committed-by: Dominik Pschenitschni <dpschen@noreply.kolaente.de>

env.config.d.ts

@@ -0,0 +1,9 @@
+declare module 'postcss-easings' {
+  import postcssEasings from 'postcss-easings'
+  export default postcssEasings
+}
+
+declare module 'postcss-easing-gradients' {
+  import postcssEasingGradients from 'postcss-easing-gradients'
+  export default postcssEasingGradients
+}

tsconfig.config.json

@@ -1,6 +1,6 @@
 {
   "extends": "@vue/tsconfig/tsconfig.node.json",
-  "include": ["vite.config.*", "vitest.config.*", "cypress.config.*"],
+  "include": ["vite.config.*", "vitest.config.*", "cypress.config.*", "env.config.d.ts"],
   "compilerOptions": {
     "composite": true,
     "types": ["node"]