Add local Sourcify instance documentation (otterscan#2017)

* Add local Sourcify instance documentation

Special thanks to spacecake8961 for creating the first draft of these docs!

* Add existing contract verification example in Forge

docs/sourcify.md

@@ -20,7 +20,7 @@ Please see our [ipfs integration docs](./ipfs.md) for more info about how we han
 
 Standard HTTP connection to their repo at https://repo.sourcify.dev/
 
-Fast access to fresh verified data. On the other hand it is less private and centralized.
+Fast access to fresh verified data. On the other hand, it is centralized and leaks all addresses you visit in Otterscan to the server.
 
 ### Local snapshot **(deprecated; soon to be removed)**
 
@@ -53,3 +53,104 @@ Rather than using the default `ipfs.io` and `repo.sourcify.dev` sites for access
 ```
 
 This is useful if you have your own Sourcify repository hosted locally, in which case all of your Otterscan activity will be private.
+
+## Run a local Sourcify instance on your dev network
+
+### Launch a local chain
+
+Launch an Otterscan-compatible local Ethereum RPC node hosting your development server.
+
+- Erigon:
+  - `./erigon --chain=dev --datadir=dev --http.api eth,erigon,trace,ots,ots2 --http.corsdomain "*" --http.vhosts "*" --mine --fakepow`
+  - Note: The Erigon devnet only supports a pre-Shanghai (pre-Merge) version of Ethereum. When compiling your contracts, you'll have to set the `evmTarget` to `london` for them to run at all on the devnet.
+    - You'll have to create a full-fledged Ethereum test network in Erigon if you want to run a modern version of the EVM.
+- Foundry's [Anvil](https://book.getfoundry.sh/reference/anvil/):
+  - `anvil`
+  - Note: Anvil does not support ots2 RPC methods, so make sure `experimental` is set to `false` in your Otterscan config.
+
+### Sourcify
+
+1. Clone the Sourcify repository:
+
+```shell
+git clone https://github.com/ethereum/sourcify.git
+```
+
+2. To add support for your local blockchain, create a JSON file `services/server/src/sourcify-chains.json`:
+```json
+{
+  "1337": {
+    "sourcifyName": "Local chain",
+    "supported": true,
+    "rpc": [
+      "http://localhost:8545"
+    ]
+  }
+}
+```
+
+You can adjust the chain ID `1337` and the RPC host `http://localhost:8545` as needed. The default chain ID for the Erigon devnet is 1337, and the default for Anvil is 31337.
+
+3. Adjust the repository URL in `ui/.env.development` since for simplicity we aren't using Sourcify's h5ai-nginx file viewer:
+
+```shell
+REACT_APP_REPOSITORY_SERVER_URL=http://localhost:5555/repository
+```
+
+4. Build all needed Sourcify components, notably the server and the UI:
+
+```shell
+npm run build:clean
+```
+
+5. Start the Sourcify server:
+
+```shell
+NODE_ENV=development npm run server:start
+```
+
+6. Start the Sourcify UI:
+
+```shell
+npm run ui:start
+```
+
+### Otterscan configuration
+
+To use the local Sourcify instance, you need to point to it in Otterscan's configuration file.
+In your Otterscan configuration JSON, specify your local Sourcify repository as the Sourcify source:
+
+```
+"sourcifySources": {
+  "ipfs": "http://localhost:5555/repository",
+  "central_server": "http://localhost:5555/repository"
+}
+```
+
+### Verifying contracts
+
+#### Verifying through the Sourcify UI
+
+You can verify contracts using the Sourcify UI by going to http://localhost:3000/#/verifier in your browser.
+
+#### Verifying with Forge
+
+1. If you deploy using a [Forge script](https://book.getfoundry.sh/reference/forge/forge-script), you should add the following contract verification arguments to the command:
+
+```shell
+forge script Deploy.s.sol .... --verify --verifier sourcify --verifier-url http://localhost:5555
+```
+
+2. If you want to deploy a contract without a script, you can use `forge create` to create the deployment transaction. Create a folder named `contracts` and put your contract files in there.
+
+Here is how you would deploy a smart contract called `MyContract` with constructor arguments `0x67b1d87101671b127f5f8714789C7192f7ad340e` and `123456`:
+
+```shell
+./forge create --verify --verifier sourcify --verifier-url http://localhost:5555/ --interactive --optimize --rpc-url http://localhost:8545/ MyContract --constructor-args 0x67b1d87101671b127f5f8714789C7192f7ad340e 123456
+```
+
+3. To verify a contract that already has been deployed, you can use `forge verify-contract`. Here is an example of a verification of the above `MyContract` contract example to address `0xADC11306fcD68F47698D66047d923a52816Ee44F`. Forge can usually infer constructor arguments automatically:
+
+```shell
+./forge verify-contract --verifier sourcify --verifier-url http://localhost:5555/ --optimizer-runs 200 --rpc-url http://localhost:8545/ 0xADC11306fcD68F47698D66047d923a52816Ee44F MyContract
+```