docs: add parentheses + change lower case to upper case in some places (#18368)

* fix: add parentheses

Add parentheses to the end `app.showAboutPanel`, because this is method.

* fix: change 'Promise<string>' to 'Promise<String>'

Change `Promise<string>` to `Promise<String>`, because this is class name.

* docs: change lower case to upper case

Change lower case in word `menu` to upper case - `Menu`, because it's method.

docs/api/app.md

@@ -688,7 +688,7 @@ To set the locale, you'll want to use a command line switch at app startup, whic
 
 ### `app.getLocaleCountryCode()`
 
-Returns `string` - User operating system's locale two-letter [ISO 3166](https://www.iso.org/iso-3166-country-codes.html) country code. The value is taken from native OS APIs.
+Returns `String` - User operating system's locale two-letter [ISO 3166](https://www.iso.org/iso-3166-country-codes.html) country code. The value is taken from native OS APIs.
 
 **Note:** When unable to detect locale country code, it returns empty string.
 

docs/api/menu.md

@@ -10,7 +10,7 @@ Creates a new menu.
 
 ### Static Methods
 
-The `menu` class has the following static methods:
+The `Menu` class has the following static methods:
 
 #### `Menu.setApplicationMenu(menu)`
 

docs/api/session.md

@@ -203,7 +203,7 @@ The `proxyBypassRules` is a comma separated list of rules described below:
 
 * `url` URL
 
-Returns `Promise<string>` - Resolves with the proxy information for `url`.
+Returns `Promise<String>` - Resolves with the proxy information for `url`.
 
 #### `ses.setDownloadPath(path)`