Speed up reading metadata from file

[argerus]

Added buffered read.

Loading a 19 MB file went from ~9 seconds -> 90 milliseconds.

[erikbosch]

To be included in 0.5

[SebastianSchildt]

That is an efficient use of 1 additional LoC :D 👍

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 50.02%. Comparing base (918f16a) to head (dd694ef).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
databroker/src/main.rs	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #84      +/-   ##
==========================================
- Coverage   50.03%   50.02%   -0.01%     
==========================================
  Files          31       31              
  Lines       11804    11805       +1     
==========================================
  Hits         5906     5906              
- Misses       5898     5899       +1     

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[SebastianSchildt]

Works for me.
lgtm 🪭