docs: guide to modify param via governance (#3832)

I created a doc to prepare for
#3827

docs/maintainers/modify-param.md

@@ -0,0 +1,48 @@
+# Modify Param
+
+This doc will guide you through the process of modifying a parameter via governance.
+
+## Prerequisites
+
+```shell
+# Verify the current parameter value
+$ celestia-appd query params subspace icahost AllowMessages
+key: AllowMessages
+subspace: icahost
+value: '["*"]'
+```
+
+## Steps
+
+```shell
+# Create a proposal.json file
+echo '{"title": "Modify ICA host allow messages", "description": "Modify ICA host allow messages", "changes": [{"subspace": "icahost", "key": "AllowMessages", "value": ["/ibc.applications.transfer.v1.MsgTransfer","/cosmos.bank.v1beta1.MsgSend","/cosmos.staking.v1beta1.MsgDelegate","/cosmos.staking.v1beta1.MsgBeginRedelegate","/cosmos.staking.v1beta1.MsgUndelegate","/cosmos.staking.v1beta1.MsgCancelUnbondingDelegation","/cosmos.distribution.v1beta1.MsgSetWithdrawAddress","/cosmos.distribution.v1beta1.MsgWithdrawDelegatorReward","/cosmos.distribution.v1beta1.MsgFundCommunityPool","/cosmos.gov.v1.MsgVote","/cosmos.feegrant.v1beta1.MsgGrantAllowance","/cosmos.feegrant.v1beta1.MsgRevokeAllowance"]}], "deposit": "10000000000utia"}' > proposal.json
+
+# Export a variable for the key that will be used to submit the proposal
+export FROM="validator"
+export FEES="210000utia"
+export GAS="auto"
+export GAS_ADJUSTMENT="1.5"
+
+# Submit the proposal
+celestia-appd tx gov submit-legacy-proposal param-change proposal.json --from $FROM --fees $FEES --gas $GAS --gas-adjustment $GAS_ADJUSTMENT --yes
+
+# Query the proposals
+celestia-appd query gov proposals --output json | jq .
+
+# Export a variable for the relevant proposal ID based on the output from the previous command
+export PROPOSAL_ID=1
+
+# Vote yes on the proposal
+celestia-appd tx gov vote $PROPOSAL_ID yes --from $FROM --fees $FEES --gas $GAS --gas-adjustment $GAS_ADJUSTMENT --yes
+```
+
+## After the proposal passes
+
+```shell
+# Verify the parameter value changed
+$ celestia-appd query params subspace icahost AllowMessages
+key: AllowMessages
+subspace: icahost
+value: '["/ibc.applications.transfer.v1.MsgTransfer","/cosmos.bank.v1beta1.MsgSend","/cosmos.staking.v1beta1.MsgDelegate","/cosmos.staking.v1beta1.MsgBeginRedelegate","/cosmos.staking.v1beta1.MsgUndelegate","/cosmos.staking.v1beta1.MsgCancelUnbondingDelegation","/cosmos.distribution.v1beta1.MsgSetWithdrawAddress","/cosmos.distribution.v1beta1.MsgWithdrawDelegatorReward","/cosmos.distribution.v1beta1.MsgFundCommunityPool","/cosmos.gov.v1.MsgVote","/cosmos.feegrant.v1beta1.MsgGrantAllowance","/cosmos.feegrant.v1beta1.MsgRevokeAllowance"]'
+```