Improve variable docs (#375)

* Improve variable docs
* Shorten the variable example

Author: patrick-tolosa

src/actions/variable.ts

@@ -8,8 +8,28 @@ import {ExpressionQualifier} from "../qualifiers/expression/ExpressionQualifier"
  * Defines a new user variable with the given value.
  * @memberOf Actions
  * @namespace Variable
+ * @example
+ * import {Cloudinary} from "@cloudinary/base/instance/Cloudinary";
+ * import {
+ *  set,
+ *  setAssetReference,
+ *  setFromContext,
+ *  setFromMetadata
+ * } from "@cloudinary/base/actions/variable";
+ * import {scale} from "@cloudinary/base/actions/resize";
+ *
+ * const yourCldInstance = new Cloudinary({cloud:{cloudName:'demo'}});
+ *
+ * const image = yourCldInstance.image('woman');
+ * image
+ *  .addVariable(set('foo1', 100))
+ *  .addVariable(setAssetReference('foo2', 'val'))
+ *  .addVariable(setFromContext('foo3', 'val'))
+ *  .addVariable(setFromMetadata('foo4', 'val'))
+ *  .resize(scale().width('$foo1').height('$foo2'))
  */
 
+
 /**
  * @summary action
  * @description Sets a new user variable with the given value.

src/actions/variable/SetAction.ts

@@ -5,7 +5,8 @@ import {ExpressionQualifier} from "../../qualifiers/expression/ExpressionQualifi
 /**
  * @description Sets a user-defined variable.
  * @memberOf Actions.Variable
- * @extends {Variable.VariableAction}
+ * @extends Variable.VariableAction
+ * @see Visit {@link Actions.Variable|Variable} for an example
  */
 class SetAction extends VariableAction {
   constructor(name: string, value: number | string | string[] | number[] | ExpressionQualifier) {

src/actions/variable/SetAssetReferenceAction.ts

@@ -4,6 +4,7 @@ import VariableAction from "./VariableAction";
  * @description Sets a user-defined variable from a file reference.
  * @memberOf Actions.Variable
  * @extends {Variable.VariableAction}
+ * @see Visit {@link Actions.Variable|Variable} for an example
  */
 class SetAssetReferenceAction extends VariableAction {
   constructor(name: string, value: string) {

src/actions/variable/SetFromContextAction.ts

@@ -4,6 +4,7 @@ import VariableAction from "./VariableAction";
  * @description Sets a user-defined variable from contextual metadata.
  * @memberOf Actions.Variable
  * @extends {Variable.VariableAction}
+ * @see Visit {@link Actions.Variable|Variable} for an example
  */
 class SetFromContextAction extends VariableAction {
   constructor(name: string, value: string) {

src/actions/variable/SetFromMetadataAction.ts

@@ -4,6 +4,7 @@ import VariableAction from "./VariableAction";
  * @description Sets a user-defined variable from structured metadata.
  * @memberOf Actions.Variable
  * @extends {Variable.VariableAction}
+ * @see Visit {@link Actions.Variable|Variable} for an example
  */
 class SetFromMetadataAction extends VariableAction {
   constructor(name: string, value: string) {

src/actions/variable/VariableAction.ts

@@ -9,6 +9,7 @@ type TypeVariableValue = number | string | ExpressionQualifier;
  * @description Defines an new user variable.
  * @memberOf Actions.Variable
  * @extends SDK.Action
+ * @see Visit {@link Actions.Variable|Variable} for an example
  */
 class VariableAction extends Action {
   private isFloat = false;