[Bicep Child Module Proposal]: `avm/res/web/site/host-name-binding`

### 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.

### Do you want to add new functionality to an existing module, publish an existing child module or both?

The functionality exists already and I want to make it available as a published child module independent from its parent module

### Parent module?

avm/res/web/site

### Module Name

avm/res/web/site/host-name-binding

### Module Details

Support setting the host name binding after site creation to allow for setting TXT record using the customDomainVerificationId output

Start by reading the existing avm/res/web/site parent module and its outputs, then compare the proposed avm/res/web/site/host-name-binding child module with the repository's module indexes and child-module conventions. Done means the existing host-name-binding functionality is independently published and supports setting the binding after site creation so the customDomainVerificationId output can be used for a TXT record.

Written by the indexing model from the issue text.