RFR: Copy edits, terminology fixes, and factual corrections to the README and the introduction [v2]

[Mark Reinhold]

> - Change “OpenJDK community” to “OpenJDK Community”
> - Omit needless words
> - s/like/such as/g
> - Fix various typos and grammatical errors
> - Tone down “contains the defacto standard” to “suggests”
> - The OpenJDK Community was launched in November 2006, not May 2007

Mark Reinhold has updated the pull request incrementally with one additional commit since the last revision:

  Fix typo

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Changes:
  - all: https://git.openjdk.java.net/guide/pull/18/files
  - new: https://git.openjdk.java.net/guide/pull/18/files/0a3f8b25..be87009e

Webrevs:
 - full: https://webrevs.openjdk.java.net/guide/18/webrev.01
 - incr: https://webrevs.openjdk.java.net/guide/18/webrev.00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/guide/pull/18.diff
  Fetch: git fetch https://git.openjdk.java.net/guide pull/18/head:pull/18

PR: https://git.openjdk.java.net/guide/pull/18