adding code completion for extends keyword in bicepparam files

[polatengin]

Closes #14985

Adding code completion for extends keyword in .bicepparam files

Current behavior;

Expected behavior;

Microsoft Reviewers: Open in CodeFlow

[github-actions]

Test this change out locally with the following install scripts (Action run 10744413944)

VSCode

• Mac/Linux

  bash <(curl -Ls https://aka.ms/bicep/nightly-vsix.sh) --run-id 10744413944

• Windows

  iex "& { $(irm https://aka.ms/bicep/nightly-vsix.ps1) } -RunId 10744413944"

Azure CLI

• Mac/Linux

  bash <(curl -Ls https://aka.ms/bicep/nightly-cli.sh) --run-id 10744413944

• Windows

  iex "& { $(irm https://aka.ms/bicep/nightly-cli.ps1) } -RunId 10744413944"

[github-actions]

Dotnet Test Results

   12 files   -     96     12 suites   - 96   3m 10s ⏱️ - 30m 57s
6 098 tests  -  4 964  6 098 ✅  -  4 964  0 💤 ±0  0 ❌ ±0 
8 238 runs   - 30 548  8 238 ✅  - 30 548  0 💤 ±0  0 ❌ ±0 

Results for commit 1e95936. ± Comparison against base commit 38ccfcc.

♻️ This comment has been updated with latest results.