feat: provide builtin types and intrinsics

[x1unix]

Description

This PR enhances textDocument/completion by providing completions for intrinsic Gno functions such as len and cap and suggestions for primitive types.

Fixes: #6

This list of LSP completions is generated by codegen-builtins tool from /tools/gendata/builtin.go.txt file.
In addition to that, Gno-flavored doc strings are converted to markdown.

Important

Source file extension is intentionally set to .txt to keep it away from go build and test commands.

List of intrinsic functions is taken from here.

Function descriptions are based on Go's from builtin package, except all mentions of channels and goroutines were removed as they aren't supported in Gno.

Updating builtin definitions

• Edit tools/gendata/builtin.go.txt
• Run make gen which will runs go generate
• Commit changes

Demo

Here is a demo from Gno Playground:

Builtin functions

Primitive types suggestion

[x1unix]

@jeronimoalbi can you please take a look?