Previously `go install` fails to install holos.
```
❯ go install github.com/holos-run/holos/cmd/holos@latest
../../go/pkg/mod/github.com/holos-run/holos@v0.86.0/internal/frontend/frontend.go:25:12: pattern holos/dist/holos/ui/index.html: no matching files found
../../go/pkg/mod/github.com/holos-run/holos@v0.86.0/doc/website/website.go:14:12: pattern all:build: no matching files found
```
This is because we do not commit required files. This patch fixes the
problem by following Rob Pike's guidance to commit generated files.
This patch also replaces the previous use of Makefile tasks to generate
code with //go:generate directives.
This means the process of keeping the source code clean is straight
forward:
```
git clone
make tools
make generate
make build
```
Refer to https://go.dev/blog/generate
> Also, if the containing package is intended for import by go get, once
> the file is generated (and tested!) it must be checked into the source
> code repository to be available to clients. - Rob Pike
