CEL function reference

[moshloop]

Create a function reference doc for all cell functions using this style: https://help.cloud66.com/docs/networking/traffic-cel-functions

Functions are listed here:

• [x] https://github.com/google/cel-spec/blob/master/doc/langdef.md#macros
• [x] https://pkg.go.dev/github.com/google/cel-go/ext#pkg-functions
• [x] https://github.com/google/cel-spec/blob/master/doc/langdef.md#list-of-standard-definitions
• [x] https://github.com/flanksource/gomplate/blob/main/funcs/cel_gen_exports.go