Add GLSL and GDScrip syntax highlighting (#1060)

Author: bemyak

.gitmodules

@@ -61,3 +61,9 @@
 [submodule "sublime/syntaxes/vue-syntax-highlight"]
 	path = sublime/syntaxes/vue-syntax-highlight
 	url = https://github.com/vuejs/vue-syntax-highlight.git
+[submodule "sublime/syntaxes/sublime-glsl"]
+	path = sublime/syntaxes/sublime-glsl
+	url = https://github.com/euler0/sublime-glsl.git
+[submodule "sublime/syntaxes/GDScript-sublime"]
+	path = sublime/syntaxes/GDScript-sublime
+	url = https://github.com/beefsack/GDScript-sublime.git

docs/content/documentation/content/syntax-highlighting.md

@@ -54,6 +54,7 @@ Here is a full list of supported languages and their short names:
 - Fortran (Modern) -> ["F03", "F08", "F90", "F95", "f03", "f08", "f90", "f95"]
 - Fortran Namelist -> ["namelist"]
 - Friendly Interactive Shell (fish) -> ["fish"]
+- GDScript -> ["gd"]
 - Generic Config -> [".dircolors", ".gitattributes", ".gitignore", ".gitmodules", ".inputrc", "Doxyfile", "cfg", "conf", "config", "dircolors", "gitattributes", "gitignore", "gitmodules", "ini", "inputrc", "mak", "mk", "pro"]
 - Git Attributes -> [".gitattributes", "attributes", "gitattributes"]
 - Git Commit -> ["COMMIT_EDITMSG", "MERGE_MSG", "TAG_EDITMSG"]
@@ -63,6 +64,7 @@ Here is a full list of supported languages and their short names:
 - Git Log -> ["gitlog"]
 - Git Mailmap -> [".mailmap", "mailmap"]
 - Git Rebase Todo -> ["git-rebase-todo"]
+- GLSL -> ["vs", "fs", "gs", "vsh", "fsh", "gsh", "vshader", "fshader", "gshader", "vert", "frag", "geom", "tesc", "tese", "comp", "glsl"]
 - Go -> ["go"]
 - GraphQL -> ["gql", "graphql"]
 - Graphviz (DOT) -> ["DOT", "dot", "gv"]