docs: add NatSpec @notice to public functions (#860)

Towards #653

Adds `@notice` tags to all public-facing and internal functions enabling
forge doc to autogenerate reference documentation for the Foundry Book.
No function signatures or behavior changed.

---------

Co-authored-by: zerosnacks <95942363+zerosnacks@users.noreply.github.com>
Co-authored-by: Amp <amp@ampcode.com>

Author: 3 people

src/StdChains.sol

@@ -65,7 +65,8 @@ abstract contract StdChains {
 
     bool private fallbackToDefaultRpcUrls = true;
 
-    // The RPC URL will be fetched from config or defaultRpcUrls if possible.
+    /// @notice Returns chain data for the given alias, with the RPC URL resolved from config or defaults.
+    /// @dev Reverts if `chainAlias` is empty or has not been registered.
     function getChain(string memory chainAlias) internal virtual returns (Chain memory chain) {
         require(bytes(chainAlias).length != 0, "StdChains getChain(string): Chain alias cannot be the empty string.");
 
@@ -79,6 +80,8 @@ abstract contract StdChains {
         chain = getChainWithUpdatedRpcUrl(chainAlias, chain);
     }
 
+    /// @notice Returns chain data for the given chain ID, with the RPC URL resolved from config or defaults.
+    /// @dev Reverts if `chainId` is `0` or has not been registered.
     function getChain(uint256 chainId) internal virtual returns (Chain memory chain) {
         require(chainId != 0, "StdChains getChain(uint256): Chain ID cannot be 0.");
         initializeStdChains();
@@ -94,7 +97,7 @@ abstract contract StdChains {
         chain = getChainWithUpdatedRpcUrl(chainAlias, chain);
     }
 
-    // set chain info, with priority to argument's rpcUrl field.
+    /// @notice Registers chain data under `chainAlias`, with priority given to the argument's `rpcUrl` field.
     function setChain(string memory chainAlias, ChainData memory chain) internal virtual {
         require(
             bytes(chainAlias).length != 0,
@@ -127,7 +130,7 @@ abstract contract StdChains {
         idToAlias[chain.chainId] = chainAlias;
     }
 
-    // set chain info, with priority to argument's rpcUrl field.
+    /// @notice Registers chain data under `chainAlias`, with priority given to the argument's `rpcUrl` field.
     function setChain(string memory chainAlias, Chain memory chain) internal virtual {
         setChain(chainAlias, ChainData({name: chain.name, chainId: chain.chainId, rpcUrl: chain.rpcUrl}));
     }
@@ -184,6 +187,7 @@ abstract contract StdChains {
         return chain;
     }
 
+    /// @notice Sets whether to fall back to default RPC URLs when no URL is configured for a chain.
     function setFallbackToDefaultRpcUrls(bool useDefault) internal {
         fallbackToDefaultRpcUrls = useDefault;
     }