jupyterlite build fails if --contents dir has any dir with a `.` in name

Description

Running jupyter lite build --contents contents fails with the following error if there is any directory whose name starts with a ..

❯ jupyter lite build --contents contents                                                                             130 ↵
static:jupyter-lite.json
.  pre_status:static:jupyter-lite.json
    tarball:         jupyterlite-app-0.1.0-beta.5.tgz 8MB
    output:          /Users/yuvipanda/code/jupyterlite-data8/tmp/_output
    lite dir:        /Users/yuvipanda/code/jupyterlite-data8/tmp
    apps:            
    sourcemaps:      True
    unused packages: True
archive:archive
contents:contents
lite:jupyter-lite.json
mathjax:status
pyodide:pyodide
serve:contents
settings:overrides
translation:translation
.  status:archive:archive
[LiteBuildApp] No archive (yet): tmp-jupyterlite.tgz
.  status:contents:contents
    contents: 1 files
.  status:lite:jupyter-lite.json
[LiteBuildApp]     jupyter-lite.(json|ipynb): 0 files
.  status:mathjax:status
     jupyter-server-mathjax: /Users/yuvipanda/.local/share/virtualenvs/textbook/lib/python3.9/site-packages/jupyter_server_mathjax/static 
     configured MathJax dir: /Users/yuvipanda/code/jupyterlite-data8/tmp/traitlets.Undefined
     effective MathJax dir: /Users/yuvipanda/.local/share/virtualenvs/textbook/lib/python3.9/site-packages/jupyter_server_mathjax/static
.  status:pyodide:pyodide
     URL: None
 archive: []
   cache: 0 files
   local: 0 files
.  status:serve:contents
    url: http://127.0.0.1:8000/
    server: tornado
    headers:
.  status:settings:overrides
    overrides.json: 0
.  status:translation:translation
    translation files: 0 files
static:output_dir
.  pre_init:static:output_dir
static:unpack
.  init:static:unpack
federated_extensions:copy:ext:jupyterlab_pygments
.  pre_build:federated_extensions:copy:ext:jupyterlab_pygments
contents:copy:.binder/wat
mathjax:copy
translation:copy
.  build:contents:copy:.binder/wat
.  build:mathjax:copy
.  build:translation:copy
contents:contents:.binder
contents:contents:.
federated_extensions:patch
mathjax:patch
.  post_build:contents:contents:.binder
TaskError - taskid:post_build:contents:contents:.binder
PythonAction Error
Traceback (most recent call last):
  File "/Users/yuvipanda/.local/share/virtualenvs/textbook/lib/python3.9/site-packages/doit/action.py", line 461, in execute
    returned_value = self.py_callable(*self.args, **kwargs)
  File "/Users/yuvipanda/.local/share/virtualenvs/textbook/lib/python3.9/site-packages/jupyterlite/addons/contents.py", line 170, in one_contents_path
    listing = fm.get(listing_path)
  File "/Users/yuvipanda/.local/share/virtualenvs/textbook/lib/python3.9/site-packages/jupyter_server/services/contents/filemanager.py", line 370, in get
    raise web.HTTPError(404, "No such file or directory: %s" % path)
tornado.web.HTTPError: HTTP 404: Not Found (No such file or directory: binder)

Reproduce

Create a directory named .binder, and just put any random file inside it.

mkdir -p contents/.binder
touch contents/.binder/runtime.txt
jupyter lite build --contents contents

Expected behavior

Context

Output from pip list:

❯ pip list                                                                                                           130 ↵
Package            Version
------------------ -------
cloudpickle        2.0.0
doit               0.36.0
entrypoints        0.4
importlib-metadata 4.11.3
jupyter-core       4.10.0
jupyterlite        0.1.0b5
pip                22.0.4
setuptools         60.10.0
traitlets          5.1.1
zipp               3.8.0

[yuvipanda]

@bollwyvl currently the build process just completely crashes if the content directory has any hidden files. I mostly just want it to not crash 😃

[yuvipanda]

@bollwyvl nvm, I got it to work! doit produced a lot of output and I was overwhelmed 😄 turns out I just needed to have yarn and node installed. I tested the PR and works 😃