Expose fuel-core version as a constant (#1473)

Necessary for FuelLabs/fuels-rs#1189. This
allows `fuels-rs` to make compatibility checks against the version of
`fuel-core` it was compiled with.

CHANGELOG.md

@@ -10,6 +10,7 @@ Description of the upcoming release here.
 
 ### Added
 
+- [#1473](https://github.com/FuelLabs/fuel-core/pull/1473): Expose fuel-core version as a constant
 - [#1469](https://github.com/FuelLabs/fuel-core/pull/1469): Added support of bloom filter for RocksDB tables and increased the block cache.
 - [#1642](https://github.com/FuelLabs/fuel-core/pull/1462): Added benchmark to measure the performance of contract state and contract ID calculation; use for gas costing.
 - [#1465](https://github.com/FuelLabs/fuel-core/pull/1465): Improvements for keygen cli and crates

crates/fuel-core/src/lib.rs

@@ -3,6 +3,8 @@
 #![deny(unused_crate_dependencies)]
 #![deny(warnings)]
 
+pub const VERSION: &str = env!("CARGO_PKG_VERSION");
+
 #[doc(no_inline)]
 pub use fuel_core_chain_config as chain_config;
 #[cfg(feature = "p2p")]