extensions: rename properties in typescript example code
After following the guide and running tsc on it, the following errors occur:
prefs.ts:14:7 - error TS2345: Argument of type '{ title: string; icon_name: string; }' is not assignable to parameter of type 'ConstructorProperties'.
Object literal may only specify known properties, but 'icon_name' does not exist in type 'ConstructorProperties'. Did you mean to write 'iconName'?
14 icon_name: 'dialog-information-symbolic',
~~~~~~~~~
prefs.ts:41:9 - error TS2345: Argument of type '{ lower: number; upper: number; step_increment: number; }' is not assignable to parameter of type 'ConstructorProperties'.
Object literal may only specify known properties, but 'step_increment' does not exist in type 'ConstructorProperties'. Did you mean to write 'stepIncrement'?
41 step_increment: 1
~~~~~~~~~~~~~~
Found 2 errors in the same file, starting at: prefs.ts:14
This will simply follow the suggestion given by typescript compiler.