Set permissions on formatter workflow

[jeskew]

Granting the formatting workflow explicit write permissions on repo contents and issues to address https://github.com/Azure/bicep/actions/runs/7771672951/job/21193245862#step:7:27

Rerunning the workflow with the changes from this PR succeeded, resulting in the a8de84f commit included in this PR.

Microsoft Reviewers: Open in CodeFlow

[github-actions]

Test this change out locally with the following install scripts (Action run 7787034499)

VSCode

• Mac/Linux

  bash <(curl -Ls https://aka.ms/bicep/nightly-vsix.sh) --run-id 7787034499

• Windows

  iex "& { $(irm https://aka.ms/bicep/nightly-vsix.ps1) } -RunId 7787034499"

Azure CLI

• Mac/Linux

  bash <(curl -Ls https://aka.ms/bicep/nightly-cli.sh) --run-id 7787034499

• Windows

  iex "& { $(irm https://aka.ms/bicep/nightly-cli.ps1) } -RunId 7787034499"

[github-actions]

Test Results

    66 files   -     31      66 suites   - 31   24m 34s ⏱️ - 28m 37s
11 009 tests  -     20  11 009 ✅  -     20  0 💤 ±0  0 ❌ ±0 
25 908 runs   - 12 861  25 908 ✅  - 12 861  0 💤 ±0  0 ❌ ±0 

Results for commit a8de84f. ± Comparison against base commit 624095f.