update new documentation and move to doc/

doc/developers-guide/developers-guide.md

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+---
+title: "Setting up a dev environment"
+slug: "developers-guide"
+excerpt: "Get up and running in your local environment with essential tools and libraries in your preferred programming language."
+hidden: false
+createdAt: "2022-11-18T14:28:23.407Z"
+updatedAt: "2023-02-08T11:42:44.759Z"
+---
+## Using `startup_regtest.sh`
+
+The Core Lightning project provides a script `startup_regtest.sh` to simulate the Lightning Network in your local dev environment. The script starts up some local nodes with bitcoind, all running on regtest and makes it easier to test things out, by hand.
+
+Navigate to `contrib` in your Core Lightning directory:
+
+```shell
+cd contrib
+```
+
+Load the script, using `source` so it can set aliases:
+
+```shell
+source contrib/startup_regtest.sh
+```
+
+Start up the nodeset:
+
+```shell
+start_ln 3
+```
+
+Connect the nodes. The `connect a b` command connects node a to b:
+
+```shell
+connect 1 2
+```
+
+When you're finished, stop:
+
+```shell
+stop_ln
+```
+
+Clean up the lightning directories:
+
+```shell
+ destroy_ln
+```
+
+
+
+## Using Polar
+
+[Polar](https://lightningpolar.com/) offers a one-click setup of Lightning Network for local app development & testing.