* Simplify rpc encode/decode messages to rpc.send/rcp.receive
* Make missing handlers message throw a warning
* Clean up formatting style in log
* Move all non-RPC loop messages to trace instead of debug
* Add format func option to log to allow newlines in per log entry

Add healthcheck for language server client, currently only checks
logging status.

The official developer documentation in in :h dev-lua-doc specifies to
use "--@" for special/magic tokens. However, this format is not
consistent with EmmyLua notation (used by some Lua language servers) nor
with the C version of the magic docstring tokens which use three comment
characters.

Further, the code base is currently split between usage of "--@",
"---@", and "--- @". In an effort to remain consistent, change all Lua
magic tokens to use "---@" and update the developer documentation
accordingly.

If vim.lsp.log is loaded the second time,
the vim.log.levels will be modified with additional
entries from 0-5.
This will cause the require to fail as level:lower does
not exists on numbered value.

fix: address typo and review comments

Adds function to notify the user like this:
`:lua vim.notify("hello user")`
embeds log levels vim.log.levels.

you can then reassign vim.notify to for instance
```
function notify_external(msg, log_level, opts)
	vim.fn.jobstart({"notify-send", msg })
end
```

while there is some controversy, stdpath('cache') looks like  a better fit for logs than stdpath('data'): you can remove logs without preventing nvim to work which fits the XDG_CACHE_HOME definition of `user specific non-essential data files`.