Support for Double Quotes / Speech Marks

A common programming language tradition is to support both double quotes ```"``` and single quotes ```'``` for text input. While I appreciate there is a lot of strong feelings (and possibly some very good technical reasons) about the differences I believe that supporting both would enable greater familiarity for those who are used to using double quotes in other languages.

Ideally what I'd like to see is functional equivalence between double and single quotes for defining strings within bicep. This should then automatically resolve into the correct ARM Template formatting. For example, the following should produce identical json.

```
resource backupVault 'Microsoft.RecoveryServices/vaults@2020-07-01' = {
name: '${CompanyPrefix}-BackupVault'
location: resourceGroup().location
properties: {
}
sku: {
name: 'RS0'
tier: 'Standard'
}
}
```

```
resource backupVault "Microsoft.RecoveryServices/vaults@2020-07-01" = {
name: "${CompanyPrefix}-BackupVault"
location: resourceGroup().location
properties: {
}
sku: {
name: "RS0"
tier: "Standard"
}
}
```

The issue names no files or tests; start by locating Bicep's string parsing entry point and the ARM template JSON emission path. Compare the single- and double-quoted examples, then verify that equivalent inputs produce identical JSON while preserving interpolation behavior.

Written by the indexing model from the issue text.