Add GC percentage calculation and report to fastq-peek.sh

[coxrs]

Description

Please include a summary of the changes being made within your PR. Please also include relevant motivation and context.

A for loop was added to count the total number of bases ($TOTAL_BASES) and concatenate the reads ($TOTAL_BASE_COUNT). All G and C basecalls in the reads are then counted ($GC_TOTAL). The GC count is then scaled to prepare for the percentage calculation ($GC_SCALED). The total number of bases and the total number of G and C basecalls are used to calculate the GC percentage of the reads ($GC_PERCENTAGE). This final percentage is reported as "GC percentage: $GC_PERCENTAGE%".

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Please also note any relevant details for your test configuration.
A small test data set was used to ensure accurate an GC percentage was calculated. Each step was also printed as it was generated to ensure that the code was accurate. The print commands have been disabled, but not removed.

Checklist:

• My code adheres to the repository style guide
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• New and existing tests pass locally with my changes