chore: added LGTM badges to readme (#1380)

[XDRAGON2002]

Closes #1380

[terriko]

Looks like you need to add 'lgtm' to the allowed spelling list.

lgtm offers two possible badges. I think the "code quality" one would probably be more meaningful to people who aren't us, so maybe we could use that one instead of the lgtm alerts number one?

Here's the code for the code quality one:

[![Language grade: Python](https://img.shields.io/lgtm/grade/python/g/intel/cve-bin-tool.svg?logo=lgtm&logoWidth=18)](https://lgtm.com/projects/g/intel/cve-bin-tool/context:python)

[codecov-commenter]

Codecov Report

Merging #1501 (440f3ae) into main (e36bc96) will decrease coverage by 0.14%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1501      +/-   ##
==========================================
- Coverage   82.40%   82.25%   -0.15%     
==========================================
  Files         279      279              
  Lines        5450     5473      +23     
  Branches      885      888       +3     
==========================================
+ Hits         4491     4502      +11     
- Misses        769      778       +9     
- Partials      190      193       +3     

Flag	Coverage Δ
longtests	82.25% <ø> (-0.15%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
cve_bin_tool/cli.py	71.75% <0.00%> (-2.87%)	⬇️
cve_bin_tool/cvedb.py	82.22% <0.00%> (-0.19%)	⬇️
cve_bin_tool/package_list_parser.py	71.66% <0.00%> (ø)
test/test_output_engine.py	98.55% <0.00%> (+0.02%)	⬆️

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[XDRAGON2002]

Added "lgtm" to list of accepted words.
I had actually added both, the alerts badge as well as the language grade badge, so as requested, removed the alerts badge.

[terriko]

Thanks!