add gitcommit grammar and language configuration

.gitmodules

@@ -170,3 +170,7 @@
 	path = helix-syntax/languages/tree-sitter-fish
 	url = https://github.com/ram02z/tree-sitter-fish
 	shallow = true
+[submodule "helix-syntax/languages/tree-sitter-gitcommit"]
+	path = helix-syntax/languages/tree-sitter-gitcommit
+	url = https://github.com/the-mikedavis/tree-sitter-gitcommit.git
+	shallow = true

book/src/generated/lang-support.md

@@ -11,6 +11,7 @@
 | dockerfile | ✓ |  |  | `docker-langserver` |
 | elixir | ✓ |  |  | `elixir-ls` |
 | fish | ✓ | ✓ | ✓ |  |
+| gitcommit | ✓ |  |  |  |
 | glsl | ✓ |  | ✓ |  |
 | go | ✓ | ✓ | ✓ | `gopls` |
 | html | ✓ |  |  |  |

helix-syntax/languages/tree-sitter-gitcommit

@@ -0,0 +1 @@
+Subproject commit 6a2ddbecd49fa8e7e1fda24d43e363cfd9171ca0

languages.toml

@@ -473,3 +473,11 @@ file-types = ["Dockerfile", "dockerfile"]
 comment-token = "#"
 indent = { tab-width = 2, unit = "  " }
 language-server = { command = "docker-langserver", args = ["--stdio"] }
+
+[[language]]
+name = "gitcommit"
+scope = "git.commitmsg"
+roots = []
+file-types = ["COMMIT_EDITMSG"]
+comment-token = "#"
+indent = { tab-width = 2, unit = "  " }