fix(input): invalid helper text (#1525)

Author: SisIvanova

src/components/input/themes/shared/input.common.scss

@@ -57,6 +57,12 @@ $theme: $base;
 }
 /* stylelint-enable */
 
+:host([invalid]) {
+    ::part(helper-text) {
+        color: var-get($theme, 'error-secondary-color');
+    }
+}
+
 :host(:disabled),
 :host([disabled]) {
     [part~='input']::placeholder {

src/components/input/themes/shared/input.indigo.scss

@@ -180,6 +180,10 @@ $transition-duration: .25s;
             background: var-get($theme, 'error-secondary-color');
         }
     }
+
+    ::part(helper-text) {
+        color: var-get($theme, 'helper-text-color');
+    }
 }
 
 :host([type='search']) {