Add JetBrains Dark syntax theme (#29)

* Add JetBrains Dark syntax theme
* Revise colouring to match GDScript JetBrains plugin in PyCharm

JetBrains-Dark.tet

@@ -0,0 +1,40 @@
+[color_theme]
+
+background_color="1e1f22ff"
+base_type_color="c87dbbff"
+brace_mismatch_color="f75464ff"
+caret_background_color="26282eff"
+caret_color="ced0d6ff"
+code_folding_color="868a91ff"
+comment_color="7a7e85ff"
+completion_background_color="2b2d30ff"
+completion_existing_color="bcbec421"
+completion_font_color="bcbec4ff"
+completion_scroll_color="6f737aff"
+completion_selected_color="393b40ff"
+control_flow_keyword_color="cf8d6dff"
+current_line_color="27282dff"
+engine_type_color="c87dbbff"
+function_color="56a8f5ff"
+keyword_color="cf8e6dff"
+line_length_guideline_color="393b40ff"
+line_number_color="4b5059ff"
+mark_color="f7546438"
+member_variable_color="c87dbbff"
+number_color="2cabb8ff"
+safe_line_number_color="4b5059ff"
+search_result_border_color="ced0d6ff"
+search_result_color="204283ff"
+selection_color="214283ff"
+string_color="6aab73ff"
+symbol_color="bcbec4ff"
+text_color="bcbec3ff"
+text_selected_color="dfe1e5ff"
+user_type_color="ce8e6dff"
+word_highlighted_color="373b39ff"
+
+gdscript/annotation_color="68a37cff"
+gdscript/function_definition_color="56a8f5ff"
+gdscript/global_function_color="c87dbbff"
+gdscript/node_path_color="b3ae60ff"
+gdscript/node_reference_color="70afbdff"

README.md

@@ -33,6 +33,7 @@ generated themes.*
 | Dracula                 |                          |
 | Gruvbox Dark            |                          |
 | Horizon                 |                          |
+| JetBrains Dark          |                          |
 | Kanagawa Dragon         |                          |
 | Kanagawa Wave           |                          |
 | Metro                   |                          |