feat(haskell): Add Haskell module (#3587)

* feat(haskell): add haskell module and implement ghc version detection

* feat(haskell): implement stack resolver version detection

* fix(haskell): handle more complex resolvers

* fix(haskell): rename resolver_version to snapshot

* fix(haskell): change default color to bold purple

* feat(haskell): add tests

* fix(haskell): format

* fix(haskell): replace incorrect `or` with `or_else`

* fix(haskell): use write_all instead of write

* fix(haskell): λ as Haskell icon by default

* fix(haskell): fix tests and add a real stack.yaml testcase

* fix(haskell): make clippy happy

src/configs/mod.rs

@@ -32,6 +32,7 @@ pub mod git_metrics;
 pub mod git_state;
 pub mod git_status;
 pub mod go;
+pub mod haskell;
 pub mod helm;
 pub mod hg_branch;
 pub mod hostname;
@@ -116,6 +117,7 @@ pub struct FullConfig<'a> {
     git_state: git_state::GitStateConfig<'a>,
     git_status: git_status::GitStatusConfig<'a>,
     golang: go::GoConfig<'a>,
+    haskell: haskell::HaskellConfig<'a>,
     helm: helm::HelmConfig<'a>,
     hg_branch: hg_branch::HgBranchConfig<'a>,
     hostname: hostname::HostnameConfig<'a>,
@@ -198,6 +200,7 @@ impl<'a> Default for FullConfig<'a> {
             git_state: Default::default(),
             git_status: Default::default(),
             golang: Default::default(),
+            haskell: Default::default(),
             helm: Default::default(),
             hg_branch: Default::default(),
             hostname: Default::default(),