text: Title: fix: improve error message for bad regex glob
  Body: A user on Matrix / Gitter was trying to run something like (simplified)
  
  ```xonsh
  ls `*`
  ```
  
  which yields
  ```
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
    File "/home/gil/mambaforge/lib/python3.10/site-packages/xonsh/built_ins.py", line 146, in pathsearch
      o = func(s)
    File "/home/gil/mambaforge/lib/python3.10/site-packages/xonsh/built_ins.py", line 121, in regexsearch
      return reglob(s)
    File "/home/gil/mambaforge/lib/python3.10/site-packages/xonsh/built_ins.py", line 88, in reglob
      return reglob(d, parts, i=0)
    File "/home/gil/mambaforge/lib/python3.10/site-packages/xonsh/built_ins.py", line 95, in reglob
      regex = re.compile(parts[i])
    File "/home/gil/mambaforge/lib/python3.10/re.py", line 251, in compile
      return _compile(pattern, flags)
    File "/home/gil/mambaforge/lib/python3.10/re.py", line 303, in _compile
      p = sre_compile.compile(pattern, flags)
    File "/home/gil/mambaforge/lib/python3.10/sre_compile.py", line 788, in compile
      p = sre_parse.parse(p, flags)
    File "/home/gil/mambaforge/lib/python3.10/sre_parse.py", line 955, in parse
      p = _parse_sub(source, state, flags & SRE_FLAG_VERBOSE, 0)
    File "/home/gil/mambaforge/lib/python3.10/sre_parse.py", line 444, in _parse_sub
      itemsappend(_parse(source, state, verbose, nested + 1,
    File "/home/gil/mambaforge/lib/python3.10/sre_parse.py", line 669, in _parse
      raise source.error("nothing to repeat",
  re.error: nothing to repeat at position 0
  ```
  
  because it should be 
  ```
  ls `.*`
  ```
  
  I don't think that there are other situations which would raise an `re.error` with the message about "position 0", so we can probably catch that error and suggest adding a `.` to the offending regular expression.
  
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