Add OpenTofu module for GitHub repo guard-rails

Manages branch protection ruleset and deployment environments for this
repository. Mirrored to JMR-dev/gh-repo-bootstrap as a reusable module
+ gh CLI extension.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

infra/github/main.tf

@@ -0,0 +1,37 @@
+data "github_repository" "this" {
+  name = var.repo_name
+}
+
+resource "github_repository_ruleset" "default_branch" {
+  repository  = data.github_repository.this.name
+  name        = var.ruleset_name
+  target      = "branch"
+  enforcement = "active"
+
+  conditions {
+    ref_name {
+      include = ["refs/heads/${var.default_branch}"]
+      exclude = []
+    }
+  }
+
+  rules {
+    deletion            = true
+    non_fast_forward    = true
+    required_signatures = var.require_signed_commits
+
+    pull_request {
+      required_approving_review_count   = var.required_reviews
+      dismiss_stale_reviews_on_push     = true
+      require_code_owner_review         = false
+      require_last_push_approval        = false
+      required_review_thread_resolution = true
+    }
+  }
+}
+
+resource "github_repository_environment" "envs" {
+  for_each    = toset(var.environments)
+  repository  = data.github_repository.this.name
+  environment = each.value
+}