Update styles.css

[Dishebh]

Fixes #1513

Checklist

• I have read the Contribution & Best practices Guide and my PR follows them.
• My branch is up-to-date with the Upstream master branch.
• I have added necessary documentation (if appropriate)
• Added Surge preview link

Changes proposed in this pull request:

• Fixed the overflow problem in small screen resolutions.

• https://pr-1514-fossasia-susper.surge.sh

[codecov]

Codecov Report

Merging #1514 into development will not change coverage.
The diff coverage is n/a.

@@             Coverage Diff              @@
##           development    #1514   +/-   ##
============================================
  Coverage        62.92%   62.92%           
============================================
  Files               51       51           
  Lines             1451     1451           
  Branches           181      181           
============================================
  Hits               913      913           
  Misses             430      430           
  Partials           108      108

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