Add the Memory-Collection and ZenDB Motoko projects (#239)

Author: tomijaga

README.md

@@ -364,6 +364,8 @@ Candid is an interface description language (IDL) for interacting with canisters
 - [Certified Blockchain](https://github.com/Factland/ic-certified-blockchain) - Certified blockchain log on on the IC. This can be validated using only the NNS public key: [Validation](https://github.com/Factland/certified-blockchain-verification).
 - [ic-oss](https://github.com/ldclabs/ic-oss) - A decentralized Object Storage Service on the IC.
 - [ic-cose](https://github.com/ldclabs/ic-cose) - A decentralized COnfiguration service with Signing and Encryption on the IC.
+- [Memory-Collection](https://github.com/NatLabs/memory-collection) - Stable Memory collections for Motoko, includes a B+Tree, Buffer and Queue.
+- [ZenDB](https://github.com/NatLabs/ZenDB) - Embedded Document DB with MongoDB style queries for large datasets for Motoko.
 
 ## Infrastructure