added gitignore file for .net proj
added gitignore file for .net proj

GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/microservices-demo,GoogleCloudPlatform/microservices-demo,GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/microservices-demo,GoogleCloudPlatform/microservices-demo,GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/microservices-demo,GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/microservices-demo,GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/microservices-demo