Change gitkeep into gitignore and move ignore up to root gitignore

I kept on getting confused on why things were being ignored in the data
dir and didn't know where to look.

.gitignore

@@ -81,6 +81,12 @@ src/bonsai/test/files/temp
 src/bonsai/test/files/basic.ifc.cache.blend
 src/bonsai/test/files/basic.ifc.cache.sqlite
 
+# bonsai data
+src/bonsai/bonsai/bim/data/build/
+src/bonsai/bonsai/bim/data/gantt/index.html
+src/bonsai/bonsai/bim/data/gantt/jsgantt.js
+src/bonsai/bonsai/bim/data/gantt/jsgantt.css
+
 src/bonsai/drawings
 src/bonsai/layouts
 
@@ -98,5 +104,6 @@ src/ifcopenshell-python/ifcopenshell/ifcopenshell_wrapper.py
 
 # Brickschema
 src/bonsai/bonsai/bim/schema/Brick.ttl
+
 bonsaiDecoratorForLoads.code-workspace
 dev_environment.bat

src/bonsai/bonsai/bim/.gitignore

@@ -1,2 +0,0 @@
-# addon writes tmp stuff directly to its dir
-/data/

src/bonsai/bonsai/bim/data/diagrams/.gitignore

@@ -0,0 +1,3 @@
+*
+!.gitignore
+!README.md

src/bonsai/bonsai/bim/data/diagrams/README.md

@@ -0,0 +1 @@
+This directory stores generated drawings in SVG format.

src/bonsai/bonsai/bim/data/schedules/.gitignore

@@ -0,0 +1,3 @@
+*
+!.gitignore
+!README.md

src/bonsai/bonsai/bim/data/schedules/README.md

@@ -0,0 +1 @@
+This directory stores generated tabular schedules in SVG format.

src/bonsai/bonsai/bim/data/sheets/.gitignore

@@ -0,0 +1,3 @@
+*
+!.gitignore
+!README.md

src/bonsai/bonsai/bim/data/sheets/README.md

@@ -0,0 +1 @@
+This directory stores generated sheets in SVG format. Sheets typically contain drawings and schedules.