Add HEEx indents and outline (#79)

These queries should match those used by HTML

Author: AlternateRT

languages/heex/indents.scm

@@ -0,0 +1,20 @@
+[
+  (start_tag ">" @end)
+  (self_closing_tag "/>" @end)
+  (start_slot ">" @end)
+  (self_closing_slot "/>" @end)
+  (start_component ">" @end)
+  (self_closing_component "/>" @end)
+] @indent
+
+[
+  (tag
+    (start_tag) @start
+    (end_tag)? @end)
+  (slot
+    (start_slot) @start
+    (end_slot)? @end)
+  (component
+    (start_component) @start
+    (end_component)? @end)
+] @indent

languages/heex/outline.scm

@@ -0,0 +1,13 @@
+(comment) @annotation
+
+[
+  (tag
+    (start_tag
+      (tag_name) @name))
+  (slot
+    (start_slot
+      (slot_name) @name))
+  (component
+    (start_component
+      (component_name) @name))
+] @item