Fix broken links in documentation (#617)

Author: per1234

Diff for: docs/getting-started.md

@@ -344,5 +344,5 @@ telemetry:
 ```
 
 [client_example]: https://github.com/arduino/arduino-cli/blob/master/client_example
-[gRPC reference]: /rpc/commands
+[gRPC reference]: ../rpc/commands
 [Prometheus]: https://prometheus.io/

Diff for: docs/index.md

@@ -9,7 +9,7 @@ CLI on your system, see the [installation] page.
 
 ## Getting started
 
-Follow the [Getting started guide](/getting-started/) to see how to use the most
+Follow the [Getting started guide] to see how to use the most
 common CLI commands available.
 
 ## Using the gRPC interface
@@ -19,7 +19,7 @@ interface of the CLI. Available services and messages are detailed in the
 [gRPC reference] pages.
 
 
-[installation]: /installation/
-[contributing]: https://github.com/arduino/arduino-cli/blob/master/CONTRIBUTING.md
+[installation]: installation.md
+[Getting started guide]: getting-started.md
 [client_example]: https://github.com/arduino/arduino-cli/blob/master/client_example
-[gRPC reference]: /rpc/commands
+[gRPC reference]: rpc/commands

Diff for: docs/installation.md

@@ -66,7 +66,7 @@ Windows   | [Nightly Windows 32 bit]   | [Nightly Windows 64 bit]   |
 Mac OSX   |                            | [Mac OSX]                  |
 
 [Nightly Linux 64 bit]: https://downloads.arduino.cc/arduino-cli/nightly/arduino-cli_nightly-latest_Linux_64bit.tar.gz
-[Nightly Windows 32 bit]: https://downloads.arduino.cc/arduino-cli/nightly/arduino-cli_nightly-latest_Linux_32bit.tar.gz
+[Nightly Linux 32 bit]: https://downloads.arduino.cc/arduino-cli/nightly/arduino-cli_nightly-latest_Linux_32bit.tar.gz
 [Nightly Linux ARM 64 bit]: https://downloads.arduino.cc/arduino-cli/nightly/arduino-cli_nightly-latest_Linux_ARM64.tar.gz
 [Nightly Linux ARM 32 bit]: https://downloads.arduino.cc/arduino-cli/nightly/arduino-cli_nightly-latest_Linux_ARMv7.tar.gz
 [Nightly Windows 64 bit]: https://downloads.arduino.cc/arduino-cli/nightly/arduino-cli_nightly-latest_Windows_64bit.zip