Ignore src/cert.pem (#425)

(cherry picked from commit 4bb7b581e961c16ffc51d48d51c70935d53c682c)
diff --git a/.npmignore b/.npmignore
index f280fa6..12ecd92 100644
--- a/.npmignore
+++ b/.npmignore
@@ -16,6 +16,7 @@
 # specific language governing permissions and limitations
 # under the License.
 #
+.idea
 .github
 build-support
 docs
@@ -33,6 +34,9 @@
 tstest.ts
 typedoc.json
 
+# pem
+src/cert.pem
+
 # license
 license-checker-config.json
 license-header.txt