[code-reflection] RFR: Fix some typos and doc improvement

[Nadeesh TV]

Fix typos and made some minor improvement in the build doc.

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Commit messages:
 - Fix some typos and doc improvement

Changes: https://git.openjdk.org/babylon/pull/766/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=766&range=00
  Stats: 24 lines in 7 files changed: 16 ins; 0 del; 8 mod
  Patch: https://git.openjdk.org/babylon/pull/766.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/766/head:pull/766

PR: https://git.openjdk.org/babylon/pull/766