.mem files are being tracked and they shouldn't be

[BrianGun]

Description

added .mem rule to .gitignore so these files won't be tracked by git.

Fixes # 204

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Test Configuration(s):

• Firmware version:
• Hardware:
• Toolchain:
• SDK:

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings

[codecov-commenter]

Codecov Report

Merging #205 (8cd869c) into main (419ef99) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #205   +/-   ##
=======================================
  Coverage   56.41%   56.41%           
=======================================
  Files          67       67           
  Lines        6388     6388           
=======================================
  Hits         3604     3604           
  Misses       2784     2784           

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