docs: add dev sessions from YouTube (#3929)

* Create development_sessions

* Rename development_sessions to videos_development_sessions

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Tendermint-Core-Development Sessions.md

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+# Tendermint-Core-Development Sessions
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+The Tendermint Core developer call is comprised of both [Interchain Foundation](http://interchain.io/) and [All in Bits](https://tendermint.com/) team members discussing the development of [Tendermint BFT](https://github.com/tendermint/tendermint) and related research. The goal of the Tendermint Core developer calls is to provide transparency into the decision making process, technical information, update cycles etc.
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+# Previous Tendermint Core Development Sessions
+
+August 2019 | Part Three: Tendermint Lite Client | [video](https://www.youtube.com/watch?v=whyL6UrKe7I&list=PLdQIb0qr3pnBbG5ZG-0gr3zM86_s8Rpqv&index=5) |
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+August 2019 | Fork Accountability | [video](https://www.youtube.com/watch?v=Jph-4PGtdPo&list=PLdQIb0qr3pnBbG5ZG-0gr3zM86_s8Rpqv&index=4) |
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+July 2019 | Part Two: Tendermint Lite Client | [video](https://www.youtube.com/watch?v=gTjG7jNNdKQ&list=PLdQIb0qr3pnBbG5ZG-0gr3zM86_s8Rpqv&index=6) |
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+July 2019 | Part One: Tendermint Lite Client | [video](https://www.youtube.com/watch?v=C6fH_sgPJzA&list=PLdQIb0qr3pnBbG5ZG-0gr3zM86_s8Rpqv&index=7) |
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+June 2019 | Testnet Deployments | [video](https://www.youtube.com/watch?v=gYA6no7tRlM&list=PLdQIb0qr3pnBbG5ZG-0gr3zM86_s8Rpqv&index=10) |
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+June 2019 | Blockchain Reactor Refactor | [video](https://www.youtube.com/watch?v=JLBGH8yxABk&list=PLdQIb0qr3pnBbG5ZG-0gr3zM86_s8Rpqv&index=11) |
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+June 2019 | Tendermint Rust Libraries | [video](https://www.youtube.com/watch?v=-WXKdyoGHwA&list=PLdQIb0qr3pnBbG5ZG-0gr3zM86_s8Rpqv&index=9) |
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+May 2019 | Merkle Tree Deep Dive | [video](https://www.youtube.com/watch?v=L3bt2Uw8ICg&list=PLdQIb0qr3pnBbG5ZG-0gr3zM86_s8Rpqv&index=8) |
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+May 2019 |Remote Signer Refactor | [video](https://www.youtube.com/watch?v=eUyXXEEuBzQ&list=PLdQIb0qr3pnBbG5ZG-0gr3zM86_s8Rpqv&index=12) |
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+May 2019 | Introduction to Ansible | [video](https://www.youtube.com/watch?v=72clQLjzPg4&list=PLdQIb0qr3pnBbG5ZG-0gr3zM86_s8Rpqv&index=14&t=0s) |
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+April 2019 | Tendermint State Sync Design Discussion | [video](https://www.youtube.com/watch?v=4k23j2QHwrM&list=PLdQIb0qr3pnBbG5ZG-0gr3zM86_s8Rpqv&index=11) |
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+April 2019 | ADR-036 - Blockchain Reactor Refactor | [video](https://www.youtube.com/watch?v=TW2xC1LwEkE&list=PLdQIb0qr3pnBbG5ZG-0gr3zM86_s8Rpqv&index=10)|
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+April 2019 | Verifying Distributed Algorithms | [video](https://www.youtube.com/watch?v=tMd4lgPVBxE&list=PLdQIb0qr3pnBbG5ZG-0gr3zM86_s8Rpqv&index=9) |
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+April 2019 | Byzantine Model Checker Presentation | [video](https://www.youtube.com/watch?v=rdXl4VCQyow&list=PLdQIb0qr3pnBbG5ZG-0gr3zM86_s8Rpqv&index=8)|
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+January 2019 | Proposer Selection in Idris | [video](https://www.youtube.com/watch?v=hWZdc9c1aH8&list=PLdQIb0qr3pnBbG5ZG-0gr3zM86_s8Rpqv&index=7)|
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+January 2019 | Current Mempool Design | [video](https://www.youtube.com/watch?v=--iGIYYiLu4&list=PLdQIb0qr3pnBbG5ZG-0gr3zM86_s8Rpqv&index=6)|
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+December 2018 | ABCI Proxy App | [video](https://www.youtube.com/watch?v=s6sQ2HOVHdo&list=PLdQIb0qr3pnBbG5ZG-0gr3zM86_s8Rpqv&index=5)|
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+October 2018| DB Performance | [video](https://www.youtube.com/watch?v=jVSNHi4l0fQ&list=PLdQIb0qr3pnBbG5ZG-0gr3zM86_s8Rpqv&index=4)|
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+October 8,2018| Alternative Mempool Algorithms| [video](https://www.youtube.com/watch?v=XxH5ZtM4vMM&list=PLdQIb0qr3pnBbG5ZG-0gr3zM86_s8Rpqv&index=2)|
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+October 2018| Tendermint Termination | [video](https://www.youtube.com/watch?v=YBZjecfjeIk&list=PLdQIb0qr3pnBbG5ZG-0gr3zM86_s8Rpqv) |