update readme/docs for arm64/armhf linux support

Author: theofficialgman

README.md

@@ -47,8 +47,8 @@ Basic HTTP authentication support|✓|✓|✓
 Proxy support|✓|✓|✓
 `amd64` support|✓|✓|✓
 `x86` support|✓|_N/A_|✗
-`arm64` support|best effort|✓|best effort, no packages
-`armhf` support|_N/A_|_N/A_|best effort, no packages
+`arm64` support|best effort|✓|✓
+`armhf` support|_N/A_|_N/A_|✓
 
 (\*) GCM guarantees support only for [the Linux distributions that are officially
 supported by dotnet][dotnet-distributions].

docs/development.md

@@ -54,7 +54,7 @@ To build from the command line, run:
 dotnet build -c LinuxDebug
 ```
 
-If you want to build for a specific architecture, you can provide `linux-x64` or `linux-arm64` as the runtime:
+If you want to build for a specific architecture, you can provide `linux-x64` or `linux-arm64` or `linux-arm` as the runtime:
 
 ```shell
 dotnet build -c LinuxDebug -r linux-arm64