Fix wrong jumps when searching for enum types

Add function s:SearchTypeDefinition to search for type definitions only.
Search only single-token identifiers in current function
Fix jumping to column
Allow jumping back with Ctrl-o after jump within function
No ':edit' to jump within current file
Match full string for digits only
Don't jump to numbers
Identifiers must not contain non-english letters
Fix (unlikely) jump to wrong position
Jump to function argument
Handle tuple assignments: let (xxx, symbol) =
Jump to enum values instead of type definitions
shellescape directory names
Ignore grep/rg errors

Because not all directories in the directory list exist.
Always reset iskeyword before returning
Add license (MIT)