Update .gitignore

Author: ocots

.gitignore

@@ -20,8 +20,13 @@ deps/src/
 docs/build/
 docs/site/
 
-# File generated by Pkg, the package manager, based on a corresponding Project.toml
-# It records a fixed state of all packages used by the project. As such, it should not be
-# committed for packages, but should be committed for applications that require a static
-# environment.
+# --------------------
+# Julia Environment Files
+# --------------------
+# Keep Project.toml; ignore Manifest.toml in packages
+!Project.toml
+# Ignore all Manifest.toml files...
 Manifest.toml
+**/Manifest.toml
+# ...except the one inside docs/src/assets
+!docs/src/assets/Manifest.toml