feat: Non-zero Default Fees (#9371)

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## Description

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closes: #9106

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docs/core/cli.md

@@ -64,10 +64,14 @@ Next is an example `rootCmd` function from the `simapp` application. It instanti
 
 `rootCmd` has a function called `initAppConfig()` which is useful for setting the application's custom configs.
 By default app uses Tendermint app config template from SDK, which can be over-written via `initAppConfig()`.
-Here's an example code to override default `appConfig` and `app.toml` template.
+Here's an example code to override default `app.toml` template.
 
 +++ https://github.com/cosmos/cosmos-sdk/blob/4eea4cafd3b8b1c2cd493886db524500c9dd745c/simapp/simd/cmd/root.go#L84-L117
 
+The `initAppConfig()` also allows overriding the default SDK's [server config](https://github.com/cosmos/cosmos-sdk/blob/4eea4cafd3b8b1c2cd493886db524500c9dd745c/server/config/config.go#L199). One example is the `min-gas-prices` config, which defines the minimum gas prices a validator is willing to accept for processing a transaction. By default, the SDK sets this parameter to `""` (empty string), which forces all validators to tweak their own `app.toml` and set a non-empty value, or else the node will halt on startup. This might not be the best UX for validators, so the chain developer can set a default `app.toml` value for validators inside this `initAppConfig()` function.
+
++++ https://github.com/cosmos/cosmos-sdk/blob/aa9b055ddb46aacd4737335a92d0b8a82d577341/simapp/simd/cmd/root.go#L101-L116
+
 The root-level `status` and `keys` subcommands are common across most applications and do not interact with application state. The bulk of an application's functionality - what users can actually _do_ with it - is enabled by its `tx` and `query` commands.
 
 ### Transaction Commands