Aligned to guideline and path optimized Android,

All were aligned accordingly and optimized to the following percentages:

Android - 31%
Bitbucket + 3%

Updated README with the new file sizes.

images/svg/bitbucket.svg

@@ -1 +1 @@
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+<svg xmlns="http://www.w3.org/2000/svg" fill="#205081" aria-label="Bitbucket" viewBox="0 0 512 512"><rect width="512" height="512" fill="#fff" rx="15%"/><path d="M422 130a10 10 0 0 0-9.9-11.7H100.5a10 10 0 0 0-10 11.7L136 409a10 10 0 0 0 9.9 8.4h221c5 0 9.2-3.5 10-8.4L422 130zM291 316.8h-69.3l-18.7-98h104.8z" fill="#2684ff"/><path d="m59.632 25.2H40.94l-3.1 18.3h-13v18.9H52c1 0 1.7-.7 1.8-1.6l5.8-35.6z" fill="url(#a)" transform="translate(89.8 85) scale(5.3285)"/><linearGradient id="a" gradientTransform="scale(-31.4) rotate(-39 -2 2)" gradientUnits="userSpaceOnUse" x2="1"><stop offset="0" stop-color="#0052cc"/><stop offset="1" stop-color="#2684ff"/></linearGradient></svg>