Add example of platform name in documentation of inputs

Even though the generic form was already provided, people who only use the IDEs will not necessarily be familiar with this notation.

Author: per1234

README.md

@@ -45,7 +45,7 @@ platforms: |
 ##### Boards Manager
 
 Keys:
-- **`name`** - (**required**) platform name in the form of `VENDOR:ARCHITECTURE`.
+- **`name`** - (**required**) platform name in the form of `VENDOR:ARCHITECTURE` (e.g., `arduino:avr`).
 - **`version`** - version of the platform to install.
   - **Default**: the latest version.
 - **`source-url`** - Boards Manager URL of the platform.
@@ -55,13 +55,13 @@ Keys:
 
 Keys:
 - **`source-path`** - (**required**) path to install as a platform. Relative paths are assumed to be relative to the root of the repository.
-- **`name`** - (**required**) platform name in the form of `VENDOR:ARCHITECTURE`.
+- **`name`** - (**required**) platform name in the form of `VENDOR:ARCHITECTURE` (e.g., `arduino:avr`).
 
 ##### Repository
 
 Keys:
 - **`source-url`** - (**required**) URL to clone the repository from. It must start with `git://` or end with `.git`.
-- **`name`** -  (**required**) platform name in the form of `VENDOR:ARCHITECTURE`.
+- **`name`** -  (**required**) platform name in the form of `VENDOR:ARCHITECTURE` (e.g., `arduino:avr`).
 - **`version`** - [Git ref](https://git-scm.com/book/en/v2/Git-Internals-Git-References) of the repository to checkout. The special version name `latest` will cause the latest tag to be used.
   - **Default**: the repository is checked out to the tip of the default branch.
 - **`source-path`** - path to install as a platform. Paths are relative to the root of the repository.
@@ -71,7 +71,7 @@ Keys:
 
 Keys:
 - **`source-url`** -  (**required**) download URL for the archive (e.g., `https://github.com/arduino/ArduinoCore-avr/archive/master.zip`).
-- **`name`** -  (**required**) platform name in the form of `VENDOR:ARCHITECTURE`.
+- **`name`** -  (**required**) platform name in the form of `VENDOR:ARCHITECTURE` (e.g., `arduino:avr`).
 - **`source-path`** - path to install as a platform. Paths are relative to the root folder of the archive, or the root of the archive if it has no root folder.
   - **Default**: root folder of the archive.