[Module Proposal]: `avm-res-signalrservice-signalr`

### Check for previous/existing GitHub issues/module proposals

- [X] I have checked for previous/existing GitHub issues/module proposals.

### Check this module doesn't already exist in the module indexes

- [X] I have checked for that this module doesn't already exist in the module indexes.

### Bicep or Terraform?

Terraform

### Module Classification?

Resource Module

### Module Name

avm-res-signalrservice-signalr

### Module Details

AVM Resource Module for SignalR Service SignalR

### Do you want to be the owner of this module?

No

### Module Owner's GitHub Username (handle)

_No response_

### (Optional) Secondary Module Owner's GitHub Username (handle)

_No response_

Begin by reviewing the repository's Terraform resource-module conventions and the existing module indexes, then compare them with the proposed avm-res-signalrservice-signalr module name and SignalR Service scope. Done means the Terraform resource module is implemented according to those conventions and added to the appropriate index; the issue does not identify specific files or tests.

Written by the indexing model from the issue text.