feat(web): custom stylesheets (#4602)

* add initial ui and api definitions for stylesheets

* proper saving

* make custom css work

* add textarea

* rebuild api

* run prettier

* add typecast

* update typings

* move css accordion to be sorted alphabetically

* set content-type properly

* rename stylesheets to theme

* fix server test

cli/src/api/open-api/api.ts

@@ -3307,6 +3307,12 @@ export interface SystemConfigDto {
      * @memberof SystemConfigDto
      */
     'storageTemplate': SystemConfigStorageTemplateDto;
+    /**
+     * 
+     * @type {SystemConfigThemeDto}
+     * @memberof SystemConfigDto
+     */
+    'theme': SystemConfigThemeDto;
     /**
      * 
      * @type {SystemConfigThumbnailDto}
@@ -3741,6 +3747,19 @@ export interface SystemConfigTemplateStorageOptionDto {
      */
     'yearOptions': Array<string>;
 }
+/**
+ * 
+ * @export
+ * @interface SystemConfigThemeDto
+ */
+export interface SystemConfigThemeDto {
+    /**
+     * 
+     * @type {string}
+     * @memberof SystemConfigThemeDto
+     */
+    'customCss': string;
+}
 /**
  * 
  * @export