Set fixed solidity-docgen version in package.json

Until OpenZeppelin/solidity-docgen#339 and
OpenZeppelin/solidity-docgen#303 are fixed

Author: Vsevo1od

package.json

@@ -40,9 +40,12 @@
     "dotenv-flow": "^3.2.0",
     "ganache-cli": "^6.12.2",
     "lodash": "^4.17.21",
-    "solidity-docgen": "^0.5.16",
+    "solidity-docgen": "https://github.com/Vsevo1od/solidity-docgen#56fcb9fae85305235d0b3af7d086cb4f7b471d3b",
     "truffle": "^5.4.8"
   },
+  "dependenciesComments": {
+    "solidity-docgen": "TODO use npm version after https://github.com/OpenZeppelin/solidity-docgen/issues/339 and https://github.com/OpenZeppelin/solidity-docgen/issues/303 are fixed"
+  },
   "devDependencies": {
     "@ethersproject/constants": "^5.4.0",
     "@nomiclabs/hardhat-ethers": "npm:hardhat-deploy-ethers@^0.3.0-beta.11",

yarn.lock

@@ -15018,10 +15018,9 @@ solidity-coverage@^0.7.17:
     shelljs "^0.8.3"
     web3-utils "^1.3.0"
 
-solidity-docgen@^0.5.16:
+"solidity-docgen@https://github.com/Vsevo1od/solidity-docgen#56fcb9fae85305235d0b3af7d086cb4f7b471d3b":
   version "0.5.16"
-  resolved "https://registry.yarnpkg.com/solidity-docgen/-/solidity-docgen-0.5.16.tgz#c12a5cac7ca656ff01b10dd832891983bb071f50"
-  integrity sha512-rFVpqSNnDGKvL68mPf4J9mEQIl+Ixy6bIz/YE6AgjBCPtrlm4KjWQhcBMQWc/LarSCenOpzhbG1tHqP9gf9kcg==
+  resolved "https://github.com/Vsevo1od/solidity-docgen#56fcb9fae85305235d0b3af7d086cb4f7b471d3b"
   dependencies:
     "@oclif/command" "^1.8.0"
     "@oclif/config" "^1.17.0"