Add Hardhat.gitignore

Hardhat (https://hardhat.org/) is a widely-used development
environment for Ethereum smart contracts. Its default project layout
generates several directories that should not be committed. This
template mirrors the .gitignore that ships in Hardhat's own
example-project (packages/example-project/.gitignore in
NomicFoundation/hardhat), limited to Hardhat-specific paths (generic
Node.js paths such as node_modules and dist are already covered by
Node.gitignore).

Rules:
- /artifacts, /cache: compiled contract output and compilation cache
- /types: TypeChain output for @nomicfoundation/hardhat-typechain (v3)
- /typechain-types: TypeChain output for @typechain/hardhat (v2)
- /ignition/deployments: Hardhat Ignition deployment output

community/Hardhat.gitignore

@@ -0,0 +1,19 @@
+# Hardhat
+# https://hardhat.org/
+#
+# Recommended: Node.gitignore
+
+# Compilation artifacts
+/artifacts
+
+# Compilation cache
+/cache
+
+# TypeChain-generated types
+# Default for @nomicfoundation/hardhat-typechain (Hardhat 3)
+/types
+# Default for @typechain/hardhat (Hardhat 2)
+/typechain-types
+
+# Hardhat Ignition deployment output
+/ignition/deployments