feat(custom_layout): add yaml file support

This commit adds support for loading custom layouts from yaml files, and
also moves the custom layout loading and validating logic into the
komorebi-core crate.

re #50

Cargo.lock

@@ -286,6 +286,12 @@ dependencies = [
  "winapi 0.3.9",
 ]
 
+[[package]]
+name = "dtoa"
+version = "0.4.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "56899898ce76aaf4a0f24d914c97ea6ed976d42fec6ad33fcbb0a1103e07b2b0"
+
 [[package]]
 name = "either"
 version = "1.6.1"
@@ -544,6 +550,7 @@ dependencies = [
  "color-eyre",
  "serde",
  "serde_json",
+ "serde_yaml",
  "strum",
 ]
 
@@ -584,6 +591,12 @@ version = "0.2.103"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "dd8f7255a17a627354f321ef0055d63b898c6fb27eff628af4d1b66b7331edf6"
 
+[[package]]
+name = "linked-hash-map"
+version = "0.5.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7fb9b38af92608140b86b693604b9ffcc5824240a484d1ecd4795bacb2fe88f3"
+
 [[package]]
 name = "lock_api"
 version = "0.4.5"
@@ -1111,6 +1124,18 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "serde_yaml"
+version = "0.8.21"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d8c608a35705a5d3cdc9fbe403147647ff34b921f8e833e49306df898f9b20af"
+dependencies = [
+ "dtoa",
+ "indexmap",
+ "serde",
+ "yaml-rust",
+]
+
 [[package]]
 name = "sharded-slab"
 version = "0.1.4"
@@ -1525,3 +1550,12 @@ dependencies = [
  "winapi 0.2.8",
  "winapi-build",
 ]
+
+[[package]]
+name = "yaml-rust"
+version = "0.4.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "56c1936c4cc7a1c9ab21a1ebb602eb942ba868cbd44a99cb7cdc5892335e1c85"
+dependencies = [
+ "linked-hash-map",
+]