reorganize docs

doc/dev/coding-tips.md

@@ -0,0 +1,19 @@
+Some not-so-obvious tricks.
+
+## Treat cookies as user-provided values
+
+I think we do pretty well here.
+
+## Jet `.Illust` vs `Illust`
+
+Be careful when you write a .jet.html template file.
+
+If you see error like `<variable name> not found in map[...]` when visiting a page, you need to add a dot before all data member access. e.g. from `Illust` to `.Illust`. gofiber doesn't mention this.
+
+In Jet, variables are accessed without a dot (`PageURL`), while data members (the `data` parameter to `Render(...)`). are accessed with a dot in front.
+
+There are 3 types of variables.
+
+- Global variables. Global functions are those.
+- Page variables. They are provided to Jet by the server.
+- Temporary variables. You use `abc := ...` to define those.