* chore: add linters and some lint fixes

Configure some golangci-lint linters to get the code quality right.
Apply the first fixes.

Next step will be to add github actions to run lint and tests in
github CI.

* chore: more lint, fixed comments and variable names. no semantic change.

* chore: add Makefile

This makefile is intended to be used as a local substitute to github
actions.

The `import` statement is now parsed. It only provides minimal
support for the `fmt` package (only `Println` symbol is defined).

This should be sufficient to pass a few tests.

Full support of package namespaces, source and binary imports will be
supported later, based on this work.

* chore: refactor to keep only the new parser and bytecode vm

* scanner: remove Token.value field

* scanner: remove scanner.kind field

* chore: move language specification in lang package

This avoid a cyclic dependency in scanner_test which can now use
the golang/GoSpec language specification for Go.

* clean code

* scanner: export scanner fields

Also parser now generate function calls, including externals.

* chore: fix lint issues

* parser: handle strings

* wip

* parser: implement support for 'if, else, else if' statements

Resolving labels in the compiler still in progress.

* parser: support if statements, improve compiler

* improve handling of functions

* improve support of local variables

* scanner: trim leading and trailing spaces

* fixes to make fibonacci work

* parser: improve README, fix function parameters parsing

As specified in the Go specification, adapted to the following:
- the scanner recognise blocks as tokens
- the scanner is multi-language: define keywords in scanner spec
- as a result, we define how to skip semi-colon insertion rather
  than how to add it.

The scanner returns a slice of pointers to tokens instead of a
slice of tokens. The parser now pass the initial node context.

Also simplify project structure. The executable is now produced in
the root directory. Work in progress.