add .gitignore and .project files

.gitignore

@@ -0,0 +1,28 @@
+*~
+.lean_trace
+*.produced.out
+*.md.lua
+*.md.lean
+*.olean
+*.clean
+*.ilean
+*.d
+a.out
+build
+GPATH
+GRTAGS
+GSYMS
+GTAGS
+Makefile
+*.cmake
+CMakeFiles/
+.projectile
+.coveralls.yml
+.lean_options
+doc/html
+make.deps
+src/emacs/dependencies
+compile_commands.json
+.ninja_deps
+.ninja_log
+build.ninja

.project

@@ -0,0 +1,10 @@
+# Lean project file
+
+# Include all .hlean files under this directory
++ *.hlean
+
+# Exclude flycheck generated temp files
+- flycheck*.hlean
+
+# Exclude emacs temp files
+- .#*.hlean