Add readMe to empty git folders

.gitignore

userMicroservice/postgres-db/pg_commit_ts/README.md

userMicroservice/postgres-db/pg_dynshmem/README.md

userMicroservice/postgres-db/pg_replslot/README.md

userMicroservice/postgres-db/pg_serial/README.md

userMicroservice/postgres-db/pg_snapshots/README.md

userMicroservice/postgres-db/pg_stat_tmp/README.md

userMicroservice/postgres-db/pg_tblspc/README.md

userMicroservice/postgres-db/pg_twophase/README.md